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" The first farmer was the first man, and all historic 
nobility rests on possession and use of land." 

— Emerson 



FARM LIFE TEXT SERIES 

EDITED BY 

KARY C. DAVIS, Ph.D., Cornell 

PROFESSOR OF AGRICULTURE, KNAPP SCHOOL OF COUNTRY LIFE, GEORGE PEABODY 

COLLEGE FOR TEACHERS, NASHVILLE, TENNESSEE; AUTHOR OF 

PRODUCTIVE FARMING, ETC. 



VOCATIONAL CHEMISTRY 

JOHN J. WILLAMAN, Ph.D. 

ASSISTANT PROFESSOR OF AGRICULTURAL BIOCHEMISTRY, SCHOOL OF AGRICULTURE, 
UNIVERSITY OF MINNESOTA 



Lippincott's Farm Manuals 

Edited by K. C. DAVIS, Ph.D., Knapp School of Country Life. Nashville, Term. 

PRODUCTIVE SWINE HUSBANDRY 1915 

By GEORGE E. DAY, B.S.A. 

PRODUCTIVE POULTRY HUSBANDRY 1919 

By HARRY R. LEWIS, B.S. 

PRODUCTIVE HORSE HUSBANDRY 1920 

By CARL W. GAY, D.V.M., B.S.A. 

PRODUCTIVE ORCHARDING 1917 

By FRED C. SEARS, M.S. 

PRODUCTIVE VEGETABLE GROWING 1918 

By JOHN W. LLOYD, M.S.A. 

PRODUCTIVE FEEDING of FARM ANIMALS 1916 

By F. W. WOLL, Ph.D. 

COMMON DISEASES OF FARM ANIMALS 1919 

By R. A. CRAIG, D.V.M. 

PRODUCTIVE FARM CROPS 1918 

By E. G. MONTGOMERY, M.A. 

PRODUCTIVE BEE KEEPING 1918 

By FRANK C. PELLETT 

PRODUCTIVE DAIRYING 1919 

By R. M. WASHBURN, M.S.A. 

INJURIOUS INSECTS AND USEFUL BIRDS 1918 

By F. L. WASHBURN, M.A. 

PRODUCTIVE SHEEP HUSBANDRY 1918 

By WALTER C. COFFEY, M.S. 

PRODUCTIVE SMALL FRUIT CULTURE 1920 

By FRED C. SEARS, M.S. 

PRODUCTIVE SOILS 1920 

By WILBERT W. WEIR, M.S. 
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FARM LIFE TEXT SERIES 
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PRODUCTIVE PLANT HUSBANDRY 1918 

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PRODUCTIVE SOILS Abridged Edition 1920 

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LABORATORY MANUALS AND NOTEBOOKS 

ON THE FOLLOWING SUBJECTS 

SOILS, By J. F. EASTMAN and K. C. DAVIS 191s POULTRY, By H. R. 
LEWIS 1918 DAIRYING, By E. L. ANTHONY 1917 FEEDING, By 
F. W. WOLL 1917 FARM CROPS, By F. W. LATHROP 1920 



Farm Life Text Series 

EDITED BY K. C. DAVIS, Ph.D. 

VOCATIONAL 
CHEMISTRY 

FOR STUDENTS OF 
AGRICULTURE AND HOME ECONOMICS 

BY 
JOHN J. WILLAMAN, Ph.D. 

ASSISTANT PROFESSOR OF AGRICULTURAL BIOCHEMISTRY, SCHOOL OF AGRICULTURE 
UNIVERSITY OF MINNESOTA 

70 ILLUSTRATIONS IN THE TEXT 



"If vain our toil, 
We ought to blame the culture, not the soil." 

Pope — Essay on Man 




PHILADELPHIA & LONDON 
J. B. LIPPINCOTT COMPANY 



ai 



5 



COPYRIGHT. 1 92 1, BY J. B. LIPPINXOTT COMPANY 



Electrotyped and Printed by J. B. Lippincott Company 
At the Washington Squat e Press, Philadelphia, U. S. A. 



APR i a 1921 

©CU611678 



PREFACE 

There are now rapidly coming into existence a large 
number of so-called agricultural high schools. They are 
located in the smaller towns or in the consolidated rural 
schools ; they teach both agricultural and home economics 
courses, as the majority of their students are from the 
farm ; they do not have large enrolments, hence mixed 
classes are conducted wherever possible. The latter con- 
dition has brought out the fact that the general sciences, 
including physics, biology, physical geography, physiol- 
ogy, and chemistry, are perfectly adapted to mixed classes, 
for the reason that these sciences are not studied as ends 
in themselves, but as means to an end. They serve as tools 
in the hands of the students for more readily grasping the 
subject matter of other more applied courses, such as soils, 
agronomy, feeding, insect control, textiles, laundering, 
cooking, and, indeed, most of the courses taught in such 
vocational high schools. They therefore serve boys and 
girls equally, not only in degree but in kind ; and the two 
can use the same text in the same class, provided the text 
supplies information of a general nature, with no one- 
sided emphasis placed on applied subject matter in either 
agriculture or home economics. 

Practically all of the present texts on elementary 
chemistry fall into one of two classes : those designed for 
students in city high schools, and those designed either for 
boys following agricultural courses or for girls in home 
economics. The present book is an attempt at meeting the 
above demand for an elementary chemistry text for mixed 
classes in the agricultural high schools. The first ten 
chapters are devoted to the fundamental facts and prin- 



vi PREFACE 

ciples of genera] chemist ry. The other chapters are aimed 

to supply the main chemical facts concerning plant and 
animal growth. These facts cover the composition of the 
soil; the chemical changes involved in its formation; the 
maintenance of soil fertility; the compounds of the plant 
and of the animal body; and the nutrition of animals. 
Besides these there are chapters on the chemistry of 
cooking and of cleaning, and on milk and its products. 
All of these items are discussed from the viewpoint of 
the chemical principles involved; working directions and 
academic facts not chemical are avoided. 

This selection of subject material was made so as to 
give nothing but that which would be of interest and value 
to both boys and girls. They are fundamentals which 
should be of the common stock of knowledge of everyone ; 
and they should be of particular use to students of those 
subjects in agriculture and home economics which have a 
chemical background. 

The style of presentation has, of course, been made 
as simple as possible. Many of the laws and subjects that 
are conventionally presented in texts on general chemistry 
are omitted; among these are ionization, dissociation, the 
gas laws, and the laws of multiple and reciprocal propor- 
tions. The writer has found that these topics are not 

ntial to an understanding of the chemistry which is 
needed by these students. 

The text is designed for a full year's course, including 
classroom and laboratory work. Where facilities are not 
available Tor the students to perform the laboratory work, 
this can be done by the instructor as demonstration. If 
only one term is given to chemistry, the text alone can be 
followed, with a limited amount of demonstration work. 
In this case the last two or three chapters may have to be 
omitted, which can be done without impairing the unity of 
tin- com 



PREFACE vii 

Realizing that no doubt many sins both of commission 
and omission are present, the writer will welcome any sug- 
gestions for the improvement of this volume. 

The writer wishes to acknowledge the aid of the 
various firms and institutions which furnished illustrative 
material: Union Sulfur Co., Fig. 39; Swift & Co., 
Figs. 15, 38, 56, 61, 64, 66, 61 ; Detroit Steel Products Co., 
Fig. 34; Harbison- Walker Eefractories Co., Figs. 31, 32; 
American Agricultural Chemical Co., Fig. 49 ; Northrup, 
King & Co., Fig. 65 ; Pittsburgh Filter Mfg. Co.,Figs. 6, 7 ; 
Florida Wood Products Co., Fig. 13 ; Acheson Graphite 
Co., Fig. 21 ; also the help of his wife in making many of 
the drawings, in correcting proof, and in giving valuable 
suggestions on points of pedagogy. 

J. J. W. 

St. Paul, Minnesota. 
August, 1920. 



CONTENTS 



CHAPTER PAGE 

I. The Field of Chemistry 1 

II. The Composition of the Universe 4 

III. The Atmosphere 16 

IV. Water 28 

V. Combustion and Fuels 44 

VI. Carbon 61 

VII. Acids, Alkalies and Salts 83 

VIII. The Light Metals 95 

IX. The Heavy Metals 112 

X. Some Common Non-metals ; 127 

XL The Agricultural Chemical Elements 147 

XII. The Soil 155 

XIII. Chemical Changes in the Soil 171 

XIV. Manures and Fertilizers 180 

XV. The Plant Body 199 

XVI. The Animal Body 226 

XVII. The Nutrition of the Animal Body 231 

XVIII. Foods and Feeds 245 

XIX. Chemistry of the Cooking and Preserving of Foods 255 

XX. Milk and its Products 270 

XXI. Chemistry of Cleaning • 280 

Appendix 285 

List of References to Supplement this Text 285 

List of Apparatus and Chemicals Required 285 

The Metric System 288 



VOCATIONAL CHEMISTRY 

CHAPTER I 
THE FIELD OF CHEMISTRY 

A Changing World. — If we stop a moment to consider 
what is the most characteristic thing about this world in 
which we live, we shall no doubt say that it is the continual 
changes that are taking place. All of our activities involve 
changes. If we walk across the room, move a book, or 
throw a stone, we have brought about changes in location 
of the various objects. If we heat a piece of iron red hot, 
we have changed its temperature and color, and even its 
size. If we strike a match, we have changed the head and 
the splinter of wood into some fumes and a little pile of 
ashes. In most places on earth the temperature changes 
considerably from summer to winter. When we eat a 
meal, within a few hours the bread and meat are converted 
into the tissues of our body. When we snap a picture with 
a camera, we change the film or plate in some way that 
enables a picture to be developed on it. Even while we 
sleep remarkable changes are going on in the body. Rocks 
slowly but surely decay and crumble and change into soil. 
A tree changes the substances of the soil into a delicious 
apple ; and if the juice of the apple is properly fermented, 
it is changed into vinegar. Our foods change considerably 
in flavor and texture during cooking. Water very fre- 
quently is changed into a solid or into a gas. Astronomers 
even tell us that the sun is changing — it is gradually cool- 
ing off. In short, we can say that everything in the uni- 
verse is continually changing. 



2 II 1 1 FIELD OF CHEMISTRY 

Physical and Chemical Changes. — It will be noticed in the 
above brief lisl of familiar changes that in some cases the 
change creates new substances; as, the digestion of food, 
the burning of the match, the growth of the apple. In 
other cases the Bubstance remains the same, but is changed 
as regards color, temperature, size or location. The first 
are Bpoken of as chemical changes, the latter as physical 
changes. Thus, a match may be whittled into an infinite 
number of fine shavings without changing the chemical 
composition of the wood in any way, for the shavings 
would >till contain the same chemical substances in the 
Bame proportions as in the original whole match. When, 
however, the match is ignited, the substances of the wood 
unite with the oxygen of the air and are converted into 
various other substances which constitute the smoke and 
the fumes and the ashes. These two cases illustrate a 
physical and a chemical change, respectively. The science 
of physics deals with physical changes, the science of 
chemistry with chemical changes. In other words, chemis- 
try is fh< si "'I 'i of the com position of substances and the 
i hang i s in composition which these, substances undergo. 

Branches of Chemistry. — It will be readily seen that the 
field of chemistry is a largo one. It involves the make-up 
i I the air, of waters, of rocks, of soils, of plants and 
animals, foods and clothing, fuels and oils, drugs and 
medicines, glass and pottery, paper, leather, building 
materials, manures— in short, every conceivable kind of 
substance. In Tact, the field of chemistry is so large that 
it i- conveniently divided into several branches, and we 
have agricultural chemistry, mineral chemistry, indus- 
trial chemistry, physiological chemistry. 

The particular things in which we are interested, of 
course, ;i re the chemical processes involved in our daily life 
in tin- home and <>n the farm. We wanl to know what hap- 
pens when silage ferments, when eggs spoil, when hay 



QUESTIONS 3 

cures, when manure becomes the humus of soil; what the 
compounds in foods are, and what becomes of them during 
digestion ; why some water is ' ' soft ' ' and some is ' 'hard' ' ; 
what the chemistry of soap-making and bluing and wash- 
ing powders is; why butter becomes rancid, cement 
hardens, and fruit juices jell. We want to be on speaking 
terms with the gases of the atmosphere, the common acids 
and salts, the elements of the soil and of plant and animal 
bodies, the constituents of coal and petroleum, and many 
other things which are vital to our everyday lives. If we 
know some of these things, it will be like going into a 
forest and being able to call the trees by name ; we shall 
appreciate the more this old world of ours with its mani- 
fold changes. But, most of all, we shall be better able to 
understand the other arts and sciences which have a 
chemical basis — nutrition, soil fertility, laundering, tex- 
tiles, metallurgy, cooking, food manufacture and preser- 
vation. If this is kept in mind, the study of the succeeding 
chapters will be more profitable. 

QUESTIONS 

1. Arrange the following into two groups, one for physical changes and the 

other for chemical changes: — 
Burning of wood. 

Contraction of steel rails in winter. 
Fermentation of sauerkraut. 
Mixing sugar and salt. 
Mixing plaster of Paris with water. 
Sawing a board in two. 
Freezing of water. 

Running milk through a cream separator. 
Grinding grain. 
Boiling an egg. 
Making soap. 

2. Explain how a knowledge of chemistry will help us to understand many- 

facts and processes in our everyday life. 

3. With what does chemistry deal ? 



CHAPTER II 
THE COMPOSITION OF THE UNIVERSE 

Chemical Elements and Compounds. — Afl W€ look about 

- made up of a large number 
of different substances — countless thousands of differ- 
ent Bubstances, in fact The soil contains a host of differ- 
ent materials; there are hundreds of different minerals 
known; then half a dozen gases in the atmosphere; 

every organ and tissue of every kind of animal and plant 
contains different substances ; our factories take the niate- 
. nd make hundreds of new drugs, chemicals 
and nt of them; petroleum is pumped from the 

ground and then separated into many different substances. 
Apparently it is a very complex world in which we live. 
Elements. — But the science of chemistry has revealed 
the following very remarkable fact : 

There art / 1st only about eighty fundamen- 

tal I it of which everything >'// the uni- 

Tliat \'<, all of the thousands of different 
materials mentioned above really involve only eighty dif- 
ferent simple substai ■ 9. T) h ■ ighty fundamental sub- 
called fl>< chemical elements. 
Compounds. — Various combinations of these elements. 
and various proportions of them, make possible the enor- 
is Dumber of different materials that wo know to exist 
in the world. Tn fact, most of these materials are corn- 
el of but a very few of the chemical elements. Thus, 
common Bait is made up of two elements, -odium and 
chlorine sugar of three, carbon, hydrogen and oxy- 

i 



EARLY CHEMISTRY 5 

gen ; water, two ; fat, three ; egg white, five ; alcohol, three ; 
gasoline, two; very few drugs contain more than four, 
and very few minerals more than seven. When two or 
more chemical elements unite to form a substance of 
definite composition, that substance is called a chemical 
compound. Thus, salt, sugar, alcohol, limestone, quinine, 
etc., are compounds, as they consist of two or more ele- 
ments united together chemically in certain definite and 
fixed proportions. 

What Chemistry Includes. — In the first chapter we 
learned that chemistry is the study of the composition 
of substances. From a little different viewpoint, we now 
see that chemistry is really a study of elements and com- 
pounds and the changes which they undergo, since every 
substance in the world is either an element or a compound, 
or a mixture of them. We can say, then, that the world 
is composed of eighty chemical elements and innumerable 
compounds of those elements. It has been the chemists ' 
job to find out what these elements are, to separate these 
various compounds, to determine what elements are in 
them and what they can be used for, and to combine ele- 
ments together to make new compounds. Thus chemical 
study has told us what gases are in the atmosphere, how 
much of each is present, and for what purpose each is 
there; it has told us what the mineral compounds of the 
soil are, and which of them the plants use ; it has told us 
how to manufacture explosives, chloroform, hydrogen 
peroxide, sugar, matches, steel, electric batteries, photo- 
graphic plates ; it has even revealed the nature of volcanic 
gases, and the composition of the sun and stars. 

Early Chemistry. — This is far different from the objects 
of chemical study three hundred years ago. At that time 
there were just two things sought for by chemists : a 
method of converting iron, lead, and other cheap metals 



(3 THE COMPOSITION OF THE I M VERSE 



into gold, and a medicine which would cure all diseases. 
They believed there were only Tour elements: earth, air, 
Rre, .-Hid water. Concerning these, we now know that they 
are doI elements at all; that the earth contains many ele- 
ments mid compounds, thai the air contains at least seven 
-u- elements and two compounds, that water is a 
compound of two elements, and that fire is not a substance, 
)>ni a violent chemical change. 

An Element Defined. — What, then, is a chemical ele- 
ment .' From what we have seen above, it will be apparent 
thai <i chemical element is a substance tvhich consists of 
hid one thing; if cannot be divided or decomposed or re- 
solved i>/f<> any sin/pin- substance. For example, sulfur 
is .in element, because so far chemists have not been able 
in separate it into two or more other substances; it con- 
sists of hut one thing. Iron, gold, oxygen, iodine, mercury, 
are elements for the same reasons. 

List of Elements. — In the accompanying table is given a 
li>t of the chemical elements now known. The commoner 
and more important ones are in black-faced type. As has 
been said, only some eighty chemical elements have been 
found: more, probably, exist, for every now and then a 
new one is discovered. Of these eighty elements, however, 
the large majority are of very rare occurrence. It can be 
Bafely said that in our ordinary daily life we never see 
Bubstances which involve over thirty of these elements; 
only about fifteen are found in the animal body, and only 
ten are absolutely necessary for plant growth. Therefore, 
the chemistry which will interest us will involve only a few 
<.f the known chemical elements. 

The Most Abundant Elements.— Furthermore, approxi- 
mately \u percent of the mass of the earth's crust, includ- 
ing the water and the ail', |g made up of but eighl cle- 
ment.-; tin- other 9eventy-tW0 put together make up only 



THE MOST ABUNDANT ELEMENTS 



about one-thirtieth of the earth. Figure 1 shows what 
these abundant elements are and the amount of each, in 
the solid earth, in the oceans, and in the air. 

No doubt by now the student has recognized that many 



OXYGEN 35.7$ 



HYDROGEN 10.7$ 



OXYGEN 49.7$ 



SILICON 26.0J& 



ALUMINUM 7 3$ 



IRON 4.1$ 



CALCIUM 3.2$ 



MAGNESIUM 2.2^ 



3% 



POTASSIUM 2.3<1 



! 



THE OTHER 



NITROGEN 75. 



OXYGEN 23.2$ 



Fig. 1. — Diagram showing the comparative abundance of the chemical elements in A, 

the oceans; B, the air; and C, the whole earth. Notice the prominent place of oxygen 

in all three, and the scarcity of nitrogen in all but the atmosphere. 

familiar substances are found in the list of chemical ele- 
ments, as iron, lead, tin, oxygen, nitrogen, phosphorus, 
sulfur, carbon. Also, many common substances such as 
starch, water, sand, salt, and glass, are not in this 
list; therefore, they must be compounds, or mixtures 
of compounds. 



THE a IMF '>ni« >N < >F THE UNIVERSE 



Table I 

• Chemical Elements With Their Symbol* and Atomic Weight? 






Aluminum 
Antimony 
Argon 

Arsenic 
Barium 

Bismuth . . . 
Boron 
Bromine . . . 
ium . . 

•n ... 
Calcium. . 
Carbon 
I . 
Chlorine 
Chromium . 

Cobalt 

( "olumbium . 
( Jopp 
I )>-»{■• 
Erbium. . . . 

mm. 
Fluorine . . . 
Gadolinium 
Gallium 

riiuni 
( Slucinum 
Gold 
Helium 
Holmium 
Hydrogen 
fiwtiiitn . 
Iodine 
Iridium 
Iron. 
Krypton 
Lanthanum 
Lead 
Lithium 

mi 
Magnesium 

Mercury 






Al 

\ 
As 

Bi 
B 
Br 
Cd 

a 

Cr 

Dv 

1. ; 
I 

Gd 

Gl 
Au 
He 
Ho 

II 

In 

I 

Ir 

Pe 

Kr 

I 

Pb 

U 

Lu 

Mg 

Mr, 

II, 



Atomic 
weight 



27.1 
120.2 

11.0 

79.9 

112.4 

132.8 

40.0 

12.0 

140.2 

35.4 

58 

58.9 
93.1 

162.5 

167.7 

152.0 

19.0 

157.3 

69.9 

72.5 

9.1 

197.2 

L0 

1.0 
114.8 

193 1 

139.0 
207.2 

I 7.', I 1 

54.9 



Name 



■*-** ■ SSgf 



Molybdenum. . 
. Milium . . . 

Neon 

Nickel 

Niton (Ra ema- 
nation ! 

Nitrogen 

im 

Oxygen 

Palladium 

Phosphorus 

Platinum 

Potassium 

odymium. 

Radium 

Rhodium 

Rubidium 

Ruthenium .... 

Samarium 

Scandium 

Selenium 

Silicon 

Silver 

Sodium 

Strontium 

Sulfur 

Tantalum 

Tellurium 

Terbium 

Thallium 

Thorium . 

Thulium 

Tin 

Titanium 

Tungsten 

Uranium 

Vanadium 
Xenon 

Ytterbium 

Yttrium 

Zinc 
Zirconium 



Mo 
Xd 
Xc 
Xi 



96.0 

144.3 
20.2 
58.6 



Xt 


222.4 


X 


14.0 


Os 


190.9 


O 


16.0 


Pd 


106.7 


P 


31.0 


Pt 


195.2 


K 


39.1 


Pr 


140.9 


Ra 


226.0 


Rh 


102.9 


Rb 


85.4 


Ru 


101.7 


Sa 


150.4 


Sc 


44.1 


Se 


79.2 


Si 


28.3 


Ar 


107.S 


Xa 


23.0 


Sr 


87.6 


S 


32.0 


Ta 


181.5 


Te 


127.5 


Tb 


159.2 


Tl 


204.0 


Th 


232.4 


Tm 


168.5 


Sd 


118.7 


Ti 


48.1 


w 


184.0 





23S.2 


V 


51.0 


.V 


130.2 


Yb 


173.5 


Yt 


88.7 


Zn 




Zr 


90.6 



MOLECULES 9 

Chemical Symbols.— One of the first things the student 
must do is to familiarize himself with the names and the 
symbols of the commonest chemical elements. The symbol 
is the short way of writing the name of the element. It 
is often the first letter, sometimes it is the first two letters, 
sometimes it is the first letter of the Latin name of the 
element. Thus is oxygen, Ca is calcium, Fe is iron 
(Latin ferrum). 

Atoms. — The symbol, however, means more than an 
abbreviation. It stands for a single particle of that ele- 
ment. This single particle is called the atom. It is the 
smallest particle of an element that can exist. It is thou- 
sands of times smaller than can be seen by even a powerful 
microscope. In studying the characteristics and proper- 
ties of an element, we therefore study the characteristics 
and properties of the atoms of that element. If an element 
is green, it is because each atom is green; if an element 
tastes sour, it is because each atom is sour. Therefore, it 
is well to realize from the beginning that the study of 
chemistry is really a study of atoms — their appearance, 
characteristics, uses, occurrence, and combinations — 
although a single atom, of course, is never handled. 

Molecules. — Xow, when two or more elements combine 
to form a compound, it must be the atoms of the elements 
that do the combining. And since the atom is the smallest 
particle of the element, these combined atoms must form 
the smallest particle of the compound. This smallest pos- 
sible particle of a compound is called the molecule. Thus, 
when one atom of sodium, represented by Xa, combines 
with one atom of chlorine, represented by CI, one molecule 
of sodium chloride or common salt is formed. This 
molecule is represented by XaCl. It is the smallest par- 
ticle of that substance that can exist. It has all the charac- 
teristics of a spoonful of salt, for the spoonful is white, 
dissolves in water, and has its characteristic taste only 



K) Till: COMPOSITION OF THE UNIVERSE 

ii-. • each minute molecule of the salt is white, dissolves 
in water, and has that taste. Just as we said that a study 
of an elemenl means the study of an atom of that element, 
Likewise the study <>!' a compound means the study of a 
molecule «>t" it. 

Chemical Equations. — There is one more thing we must 
consider in this chapter, and that is the method of writing 
chemical changes. In the above example, the formation of 
sodium chloride, or common salt, could be written thus : 

sodium combined with chlorine forms sodium chloride 
or it could be written : 

sodium -+- chlorine = sodium chloride. 

It is very much simpler, however, to write it thus: 

Nfa + CI = XaCl 

Usually the latter two forms are combined: 

tfa - CI = XaCl 
-odium chlorine sodium chloride 

Such a method of recording a chemical change is called 
a < hi mical < <i'i<ilj<n). The above equation tells us that one 
atom of -odium combines with one atom of chlorine to 
form one molecule of sodium chloride. The formation of 
quicklime would be shown in the following equation: 

4- = CaO 

calcium oxygen calcium oxide (quicklime) 

Tin- formation of water demands a little different 
treatment, since two atoms of hydrogen combine with 
one of oxygen : 

2H + O = IT.O 

hydrogen oxygen hydrogen oxide (water) 

It will Denoted thai the2is written hrfore the H when the 
letter Btandfl alone as an element, but that it is written 
after and below the II in the molecule. In the molecule of 
II I >. there are two atoms of hydrogen and one of oxygen; 
the figure I, however, i> not written, but is always under- 



MOLECULAR WEIGHTS 11 

stood. Likewise in the formula for calcium oxide, CaO, 
there is one atom of calcium and one atom of oxygen, 
although the figures are not written. 

Atomic Weights. — From the very beginning of modern 
chemistry it was recognized that, although one atom of Na 
combines with one atom of CI to form NaCl, it is not one 
ounce of Na to one ounce of CI; nor does H 2 repre- 
sent two ounces of H combined with one of 0. It was 
found that all elements combine in different proportions 
by weight and hence that the atoms of the different ele-< 
merits weigh different amounts. For example, an atom 
of oxygen weighs 16 times as much as an atom of hydro- 
gen; an atom of sulfur twice as much as an atom of 
oxygen. By extremely careful methods of study, the rela- 
tive weights of all the elements have been determined. 
Since hydrogen is found to have the lightest atom of all 
the chemical elements, its relative weight is taken as 1. 
And since the oxygen atom is 16 times heavier, its weight 
is taken as 16 ; and as sulfur is twice as heavy as oxygen, 
it must be 32 times as heavy as hydrogen, and its relative 
weight is taken as 32. 

In like manner, every element has been given such a 
relative weight, and these weights are Jcnoivn as the atomic 
weights. They are given in Table I. The atomic weight 
is not the weight of the atom in ounces or grams or any 
other unit of weight; it simply represents the number of 
times the atom of that element is heavier than the atom 
of hydrogen. 

Molecular Weights. — The atomic weight of sodium is 
23 ; that of chlorine is 35.5. In the equation 

Na + Cl = NaCl 

23 parts by weight of Na combine w^ith 35.5 parts by 
weight of chlorine, forming 58.5 parts by weight of NaCl. 
It makes no difference whether we use 23 and 35.5 ounces, 



12 THE COMPOSITION OF THE UNIVERSE 

or 23 and 35.5 grams, or tons; the relation still holds, and 
there would result 58.5 ounces, grams, or tons of XaCL 
The number 58.5 ia called the molecular weight; it is the 
the atomic weights in the molecule. 

What an Equation Represents. — We are now in a posi- 
tion to examine carefully the full meaning of a chemical 
equation. Since all chemical changes can be written in 
the form of equations, and since the science of chemistry 
deals with chemical changes or reactions, it is very neces- 
Bary at the outset of our course thoroughly to understand 
and appreciate the meaning of such equations. The ex- 
amples given above are very simple; many, however, are 
very complicated. For a simple example, consider the 
chemical change involved in the burning of a piece of 
charcoal Charcoal is carbon, and when it burns it com- 
bines with oxygen thus: 

I + •_>«> = co 2 

carbon oxygen carbon dioxide (carbonic acid gas) 

If, however, we try to represent in an equation the burn- 
ing of a piece of wood, we meet with complications. The 
wood is not a single substance like charcoal; it contains 
dozens of different substances, each of which combines 
with oxygen in its own particular way, and hence would 
demand an equation all of its own. Therefore, not one 
equation, but many of them would be necessary to prop- 
erly express the chemical changes involved in the burning 
of a piece of wood. Only one chemical change at a time, 
then, can In- considered in writing a chemical equation. 

It will be noticed in all of the above examples that the 
equation tells us what substances unite, or " react," and 
what Bubc or Bubstances are formed. It also gives us 

the formula of each substance; that is, the kinds of atoms 
and the number of each, in each molecule. Thus the for- 
mula of carbon dioxide, commonly known as carbonic acid 



QUESTIONS 13 

gas, is C0 2 , which means that the molecule of carbon 
dioxide consists of one atom of carbon and two atoms of 
oxygen. Every compound has a chemical name. The 
chemical name tells of what the compound is made. Thus, 
the chemical name for water is hydrogen oxide ; the latter 
we get from the formula H 2 0. The chemical name for 
common salt is sodium chloride, and this name we get 
from the formula NaCl. The system of chemical names 
will be explained later. Furthermore, an equation tells 
us the relative quantities of the substances involved. Thus 
the above equation shows that 12 grams, or ounces, or 
tons, of carbon combine with 2 X 16, or 32, grams, ounces, 
or tons of oxygen, to form 44 grams, ounces, or tons of 
carbon dioxide. 

Important Meanings of an Equation. — The following 
points, then, should be kept in mind as regards a chemi- 
cal equation : 

1. A chemical equation represents a single chemi- 
cal reaction. 

2. The equation tells us what substances react with 
each other, and what products are formed. 

3. It tells us how many atoms and molecules of each 
substance are involved. 

4. It tells us the formula of each substance, and the 
formula enables us to give the compound a chemical name. 

5. It tells us the quantities by weight of each substance 
involved in the reaction. 

QUESTIONS 

1. How does a chemist prove whether a substance is an element or 

a compound? 

2. How many elements are there in the world ? How many compounds ? 

3. Name ten elements and ten compounds. 

4. How can you find out from this chapter which of the following are ele- 

ments and which are compounds? Tin, granite, soap, Epsom salts, 
blue vitriol, nitrogen, silver. 

5. Name some of the things that chemistry has taught us and has produced 

for us. 



u Till: COMPOSITION OF THE UNIVERSE 

ft, What is the moat abundant chemical element in the air! In the ocean? 
In the cruel of the earth! 

7. What i- the exact meaning of the formula of a compound? 

B w ; iat Ave things does each of the following equations tell us? 

g + 20 = SO, 

sulfur oxygon sulfur dioxide 

B + CI = HC1 

hydrogen chlorine hydrogen chloride (muriatic acid) 

N 4- 3H = Ml 
nitrogen hydrogen nitrogen hydride (ammonia) 

•_» iv -f 3 = FeA, 
iron oxygen iron oxide (iron rust) 

!». Why Bhould we learn to know substances by their chemical name as 
well as by their common name? 

LABORATORY EXPERIMENTS 

i. To Study Examples of Physical Changes.— (a) Weigh out 5 g. of 
BUgar, and dissolve in 25 c.c. of water in a porcelain evaporating dish or a 
Evaporate carefully to dryness, using a water bath if possible. Care- 
fully scrape out the residue and weigh it. Has the treatment with water 
changed the amount of sugar! Test it as follows: Take portions of it, and 
portions of the original sugar and compare their taste. Examine them under 
the lens. Heat them in test tubes. What changes did the sugar undergo? 
Arc these changes physical or chemical! How does dissolving in water affect 
sugar! What does this experiment teach us concerning the process of ob- 
taining granulated sugar from sugar beets and sugar cane? 

(hi Heat a piece of glas< rod or tubing very gently at first and then 

strongly. What changes has the piece of glass undergone? Mention 

Other examples of >imilar changes. 

(c) Place a few flakes of iodine in a small porcelain dish, and cover the 

dish with a --mall piece of glass. Stand the dish on asbestos on a tripod or 

stand and bent very gently and slowly. What becomes of the iodine? 

What kind of a change has it undergone! How do you know? 

2. To Study Examples of Chemical Change. — (a) Heat a little sugar 
in a teat tube, ;it first gently, then strongly. What kind of a change has 

H"u <|<» you know! What remains in the tube? 
(b) Heat a similar amount of sugar in an open dish, at first gently, 
and then with the hottest flame. How does this change compare with that 
in (a>:- What wential difference between them! 

3. To Distinguish Between Chemical and Physical Changes. — 

one powdered sulfur with a magnet. Test it- solubility in carbon 
bisulfide by mixing a little sulfur with the liquid, pouring out some of 
tho olonr solution onto a watch glass, and then evaporating down in a 
warm place. },ut nun" fmm flames 1 Test a little of the sulfur in a test tube 
with dilute hydrochloric acid. 

Make thi on gome powdered iron. 



LABORATORY EXPERIMENTS 15 

(c) With a mortar and pestle, thoroughly mix about 3 g. of sulfur and 
5 g. of iron powder. Describe the changes that have taken place. Test small 
portions of this mixture with the carbon disulfide, with the magnet, and 
with hydrochloric acid. If the sulfur appears to stick to the magnet, gentle 
shaking will release it. Has a physical or a chemical change taken place in 
the iron and in the sulfur? 

( d ) Place the rest of the mixture from ( c ) in a test tube, and carefully 
heat until the mass begins to glow like a red-hot coal. When the action has 
ceased, break the tube by immersing in water, pick out the fused iron and 
sulfur, and perform the tests as in (a), (b) and (c). What type of change 
has taken place? How do you know? What substance has, been formed? 
State all the physical changes that took place during this experiment, then 
all the chemical, and name the products formed during each chemical re- 
action. Write these reactions in the form of equations. 

4. To Study Examples of Chemical Combination. — (To be done by 
instructor.) (a) In a porcelain dish, or on a piece of asbestos, place to- 
gether a small piece of phosphorus (never handle with the hands) and a 
few flakes of iodine. What product is formed? Write the reaction in the 
form of an equation. Why is this, reaction called combination? 

(b) By means of tongs hold a piece of magnesium ribbon in the flame. 
Describe the result. What is the "smoke"? Write the equation. Why is 
this a combination change? 

(c) State three other examples of chemical combination. 

(d) What reactions in experiments 2 and 3 are chemical combinations? 

5. To Study Examples of Chemical Decomposition. — (a) Heat a 
few crystals of copper sulfate (blue vitriol) in a porcelain dish. What 
change in form have the crystals undergone? What is the white substance 
left? Write the equation. Change this example of decomposition into one 
of combination by adding a few drops of water to the white residue and 
thus restoring the blue vitriol. 

(b) What reaction in experiment 2 is decomposition? 

(c) Is the burning of a match combination or decomposition? Why?' 



CHAPTER III 

THE ATMOSPHERE 

Taking up now some of the commonest elements and 
their compounds, so as to familiarize ourselves with the 
chemical nature of the world about us, we naturally first 
look t<» the atmosphere in which we live, because the atmos- 
phere is a mixture of two very important elements, oxygen 
and nitrogen, and at least two important compounds, car- 
hon dioxide 1 and water vapor. 

Nature of the Atmosphere. — Our atmosphere is a thin 
layer of gas surrounding the earth. It is thin in propor- 
tion to the diameter of the earth; for while the latter is 
s < if i' ) miles, the air is probably not over 200 or 300 miles in 
depth, and the greater bulk of it by weight is within the 
first forty or fifty miles. In fact, we know that mountain 
climbers and aviators have great difficulty in breathing 
when they rise to even four miles. These facts show that 
air has weight and is pulled towards the surface of the 
earth by the force of gravity. The actual weight of air 
over every square inch of surface at sea level is about 15 
pounds, or over 41,000 tons per acre. This weight of the 
air is very important, as it propels our windmills and 
sailing vessels, and forces the water up into our pumps 
when the valves make a partial vacuum. 

The Air and Mixture of Gases.— That the air is not a 
single substance hut a mixture can be proved in two inter- 
esting ways. 'Hie fust is to allow a piece of phosphorus to 
hum in an enclosed volume of air, as under a bell jar* 
I Pig. 2). The phosphorus will unite with the oxygen of 

• experiment 8 ;a end of chapter, 

Hi 



NATURE OF THE ATMOSPHERE 



17 



the air as long as there is any present, forming phosphorus 
pent oxide according to the following equation : 



2P +50 = 

phosphorus oxygen 



P 2 5 

phosphorus pentoxide 



This compound is the white fumes which gradually dis- 
solve in the water and disappear. The gas now left in the 
bell jar is practically all nitro- 
gen, w T ith traces of carbon di- 
oxide and water vapor. It will 
be noticed that the water has 
risen in the jar to take the 
place of the oxygen removed. 
If the oxygen of the air had 
been combined with the nitro- 
gen, the phosphorus could not 
have removed it. This proves 
that the oxygen, nitrogen and 
other gases are simply mixed 
together, like the mixture of 
gasoline vapor and air in a 
carburetor. 

The other proof that air is 
a mixture is the fact that the 
various constituents have dif- 
ferent densities, and the heav- 
ier ones have a tendency to 
settle towards the surface of 
the earth. This is shown in Table II, which gives the 
analysis of air at different heights above the surface of 
the earth. Carbon dioxide being the heaviest, is found 
only in the lower layers of the atmosphere ; and nitrogen 
being the lightest, is practically the only one found in the 
upper layers. If air were a compound of these gases, it 
would be of the same composition throughout. 

2 




Fig. 2. — Apparatus used in demonstrat- 
ing that air is a mixture of gases. The 
burning piece of phosphorus on the cork 
under the bell jar removes the oxygen 
from the enclosed air. This creates a 
partial vacuum, and the water rises in 
the jar. If all the oxygen were removed, 
the water would occupy about one-fifth 
of the space under the jar. 



Lri 



THE ATMOSPHERE 



Table II 
Composition of the Atmosphere at Different Levels 





1 urtt B 

.surface 
P 1 cent 


6 miles 
per c< ill 


12 miles 
per cent 


30 miles 
per cent 


GO miles 
per cent 


Nitrogen 


78.0 
21.0 
0.94 

0.03 


81.1 
18.3 
0.58 
0.02 


8G.0 
13.8 
0.22 
0.01 


89.6 
10.3 
0.07 
0.00 


95.3 


« bcygen 

M 


4.6 
0.00 


m dioxide 


0.00 







Carbon Dioxide. — Let us now consider the individual 
gases of the atmosphere. Argon is one of a group of 
rare gases thai are of scientific interest only, and need 
not be discussed here. Carbon dioxide is the product 
formed when carbon, or any compound of carbon, burns. 
ii is also produced in animal bodies by the combustion 
of the food materials, and is breathed out of the lungs 
in considerable quantities. It is commonly called car- 
bonic acid gas. As can be seen in the accompanying table, 
there is bu1 a very small amount of it in the air, 0.03 per 
(•"■lit. This means that in 10,000 quarts of air there are 
only 3 quarts of carbon dioxide. The carbon dioxide gets 
into the air in considerable amount from the burning of 
fuel. When one considers the millions of tons of coal 
and other i'ii(l that are burned in the world every year, it 
may seem remarkable that the amount of carbon dioxide 
in the air does not increase rapidly. Two things should be 
kepi in mind in this regard, however. The first is, that a 
few million tons of carbon dioxide really form but a very 
Bmall trad ion of the total bulk of our atmosphere. (See 
question 5 .-it end of chapter.) The second is, that plants 
are continually taking carbon dioxide from the air and 
using it to build up their tissues; and when it is remem- 
'I thai the ares oi the earth's surface covered by 
green vegetation is thousands of times greater than the 
area covered by cities and furnaces, it will be readily 



PROPERTIES OF NITROGEN 19 

understood bow nature maintains the balance of carbon 
dioxide in the air. The amount of carbon abstracted from 
the air by plants is really enormous. For example, an 
acre of mature corn contains about 6200 pounds of dry 
material, and nearly half of this is carbon. Thus 3000 
pounds of carbon are abstracted from the air by an acre 
of this plant in a single season. Two or three heavy 
cuttings of alfalfa may contain 5000 pounds of carbon 
per acre. It should be mentioned here that many analyses 
of air, from many parts of the earth, at various seasons 
of the year, show but extremely small variations from 
0.03 per cent of carbon dioxide. Air over cities usually 
shows higher percentages than air over the country. The 
chemistry of carbon dioxide will be discussed more fully 
in Chapter VI. 

Nitrogen. — This gas occupies nearly four-fifths of the 
air by volume, or three-fourths of it by weight. This is 
clearly shown in Figure 2. There is thus an enormous 
mass of it altogether in the air. Since, however, there is 
only a small trace of it in the solid portion of the earth, 
that is in the soil, rocks, and water, nitrogen really occu- 
pies but 0.02 per cent of the total weight of the earth. 
Its compounds, however, are of extreme importance ; they 
enter into the composition of every plant and animal cell; 
egg white, lean meat, the curd of milk are spoken of as 
nitrogenous foods; practically all high explosives and 
artificial dyes are compounds of nitrogen ; in the soil it is 
usually found in very small amounts, and is the most 
costly fertilizer element. All through this course, there- 
fore, we shall have occasion to talk about the compounds 
of nitrogen. 

Properties of Nitrogen.— In the air the nitrogen is not 
combined as a compound; it exists as free nitrogen. In 
this condition it is a rather uninteresting element chemi- 
cally. It is very inert, undergoing chemical changes and 



20 THE ATMOSPHERE 

entering into chemical reactions with great difficulty. As 
was Been in the bell-jar experiment a few pages back, it 
is a colorless, odorless gas. It will not dissolve readily 
in chemicals, it will not burn, it will not support combus- 
tion, it cannot be experimented with in any way like many 
other gases which we shall study. 

Nitric Acid. — There are a few violent ways in which it 
can be made to unite with oxygen, the most important of 
which is the electric spark. When lightning discharges 
through the clouds in a storm, a considerable amount of 
nitrogen and oxygen combine to form nitrogen pentoxide, 
according to this equation : 

2 N -f :» ( ) = X.O, 

aitrogen oxygen nitrogen pentoxide 

This nitrogen pentoxide then dissolves in the rain water to 
form nitric acid, thus : 

No + HX> = 2HXO, 

nitrogen pentoxide water nitric acid 

Some ammonia, XII ,, is formed by the electric discharge 
at tin- same time, and this combines with the nitric acid to 
form ammonium nitrate. Both the nitric acid and the 
ammonia are very valuable and quick-acting fertilizers, 
and it i> these which cause the wonderful greening 
ass within a shorl time after a thunder shower. It 
been found that Prom 5 to 8 pounds of nitrogen per 
acre are brought down by rain each year in this manner. 
Ineers and chemists, working together, have devised 
machines which imitate this process of nature for produc- 
ing nitric acid. In Norway, where electric power is plen- 
tiful and cheap, enormons amounts of nitric acid are made 
in this way. And it is claimed that Germany could not 
continued the World War so many years if she had 
not utilized this proe< *ss for making nitric acid, needed in 
large quantities for making high explosives. 



FREE VERSUS COMBINED NITROGEN 21 

Explosives. — In these nitrogenous explosives advantage 
is taken of the fact that since nitrogen forms compounds 
with great difficulty, these compounds are also easily de- 
composed — by flame or even by concussion. Imagine a 
barrel of nitrogen gas combined into a solid chemical the 
size of a baseball ; and this chemical enclosed in a cannon 
barrel and decomposed by a percussion cap. Within a 
fraction of a second the nitrogen is liberated as a gas, and 
it tries to expand to its original volume of a barrel; at 
the same time the great heat developed makes it expand 
many times more than this. We thus get an idea of the 
enormous pressure developed behind a cannon ball by the 
decomposition of an unstable compound of nitrogen. 

Free Versus Combined Nitrogen. — Although all plants 
and animals require compounds of nitrogen as food, they 
cannot avail themselves of the uncombined nitrogen of 
the air. We breathe great quantities of nitrogen into our 
lungs, but it is all breathed out again unchanged and 
unabsorbed. A potato plant may be starving for nitrogen 
in a poor soil, and still be unable to utilize the tons of 
nitrogen blowing around it in the air. One class of plants, 
the legumes, to which the peas, beans, and clover belong, 
can make use of atmospheric nitrogen when they have 
certain bacteria living in little nodules or lumps on their 
roots. We shall have more to say about this when we 
come to the question of plant nutrition. 

Since nitrogen as an element, then, is so inactive, its 
chief purpose in the air is to dilute the oxygen. This 
brings us to the next most abundant gas of the atmosphere, 
oxygen, the "elixir of life," the "vitalizing element. " 

Combustion. — Everyone knows that any substance must 
have air in order to burn : exclude air from a tire, and it 
goes out; exclude air from the lungs of an animal, and 
combustion in the body ceases. In other words, air sup- 
ports combustion ; it enables a substance to burn when once 



THE ATMOSPHERE 

rly everyone now knows that it is the oxygen 
pari of the air that really supports combustion. This fact 
scovered in 1774 l>y Joseph Priestley, an English 
chemist, and this discovery of oxygen is one of the great 
landmarks in the history of chemistry. Combustion is no 
doubt one of the most important single chemical reactions 
thai is known. A> we now know it. ordinary combustion is 

' the production of heat. 
Combustion may vary in speed and violence from the 
blazing of a splinter or the instantaneous explosion of 

►line vapor, to the slow combustion of the food in our 
bodies, or the even slower burning of food in the bodies 

sold-blooded snakes and fish. Combustion furnishes 
the world with most of its energy; the combustion of coal, 

1. and petroleum products keeps us warm, runs our 
engines and machinery, hauls us on trains or on boats; 
and every Living animal gets its energy to live and to do 
work by the combustion of fuel in its body. We cannot 
appreciate too highly the importance of this universal 
chemical reaction. We have already given several exam- 
ples of simple combustion, as the burning of sulfur, of 
hydrogen, and of phosphorus; more complex examples 
will be given from time to time. 

Oxygen in the Air.— Let us emphasize again here, that 

on the -] per cent of oxygen in the air that we are 
dependent for the support of this combustion. If the air 
were al] sad of only one-fifth, combustion 

would proceed many times more rapidly. An interesting 
demonstration of this is the fact that iron and aluminum 
burn brilliantly in a bottle of oxygen. A mouse put into 
a bottle of oxygen burns up its fuel faster than it can 

si more food for fuel, and it booh dies. Advanl 

been taken of this increased respiration in the body 
with an increased supply of oxygen in the machine called 



PLANTS AND CARBON DIOXIDE 



23 



the pulmotor, which forces oxygen into the lungs of per- 
sons who have suffocated by water or by gas. 

Plants and Carbon Dioxide. — In discussing carbon diox- 
ide, it was pointed out that millions of tons of it are 
thrown into the air from our furnaces ; that it does not 
accumulate in the air, however, because plants are con- 
tinually abstracting it to build up their tissues. But whv 




Fig. 3. — An open fire-place. In this form of heating arrangement only a very small per- 
centage of the developed heat radiates into the room; but it is a cheerful heating plant, and 
the open flue causes continuous ventilation. 

does not the enormous consumption of oxygen in our 
furnaces soon deplete the supply in the air? Chemical 
analysis shows that the oxygen is not being depleted ; that 
it remains constant at about 21 per cent of the air. For 
the answer to this question we must go to the plants, as 
we did in the case of carbon dioxide. When a plant 
absorbs carbon dioxide, it is the carbon part of it that is 
used. The carbon is combined with water to form the 



_M THE ATMOSPHERE 

well-known class of substances called carbohydrates (the 
aame indicating that they are compounds of carbon and 
water). Starch, sugar, and cellulose fibres of plants are 
examples of such carbohydrates. Let us use starch, 
( ', II ..,( ) ,, to illustrate this chemical reaction in the form 
of an equation : 

5 H..O + 6COs = C 6 H 10 O 8 + 6 0, 

water carbon dioxide starch oxygen 

The equation tells us that six atoms of carbon from the 
carbon dioxide combine with five molecules of water to 
form one molecule of starch. In taking the carbon out 
of the carbon dioxide, there is left the six 2 groups. 
Since the plant has no use for all this oxygen, it exhales 
it hack into the atmosphere. In other words, for all the 
carbon dioxide that the plant absorbs from the air, there 
is a corresponding amount of free oxygen returned to it. 
In this way the balance between them is maintained. 

Photosynthesis. — It should be remembered that only in 
the green pa its of plants, and only in sunlight, can this 
remarkable transformation of carbon dioxide and water 
into starch be carried on. This process is called photo- 
synthesis, which means "manufacturing by means of 
light." The plant uses the starch, then, to build up all 
the other substances of its body. Hence photosynthesis 
is the fundamental chemical reaction behind all crop pro- 
duction, forest growth, and coal formation (since coal is 
decayed vegetable matter). We can now understand the 
tremendous importance of the trace of carbon dioxide 
in the air. Since photosynthesis is so important, it will 
be mentioned several times in this course. At the present 
moment we are interested in it because it is helping to 
maintain constanl amounts of carbon dioxide and of 
•'•II in our atmosphere. 

Oxidation.— The chemistry of oxygen is far more inter- 
esting than thai of nitrogen. Whereas the latter is very 



OXIDATION 25 

inactive, oxygen is very active. It combines readily with 
practically all the other elements. Combined with silicon 
in the form of silicon dioxide, or quartz, it constitutes 
three-fourths of the weight of the earth. Combined with 
hydrogen, it forms water, which makes up three-fifths of 
our bodies, and covers two-thirds of the area of the globe. 
The chemical reaction involved ivhen anything combines 
with oxygen is called oxidation. Hence combustion %s- 




Fig. 4. — Apparatus for the preparation of oxygen. 

rapid oxidation. Oxidation, the compounds of oxygen, 
fuels, and related subjects, are so very important that a 
separate chapter is reserved for them. 

As regards the other characteristics and properties of 
oxygen, we know that it is odorless, colorless, and taste- 
less; Table II shows us that it is a little heavier than 
nitrogen, but lighter than carbon dioxide. It dissolves 
in water to an appreciable extent, and it is this dissolved 
oxygen that fish utilize when they "breathe water."' 



THE ATMOSPHERE 

Other Constituents of the Air. — We have HOW discussed 
argon, nitrogen, ammonia, nitric acid, carbon dioxide and 
oxygen as being the constituents of onr atmosphere. Be- 
sides these, we know thai there Ls water vapor in varying 
quantities, and thai there is a continual transfer of water 
from the earth to the air by evaporation, and from the air 
to the earth as rain. Since, however, rain, snow, clouds, 
dew, etc., are physical phenomena and not chemical, they 
cannot he discussed here. Very often there are abnormal 
constituents of the air due to our civilization: fumes from 
factories, smokestacks, and smelters are sometimes 
abundant enough to cause harm to both animals and 
plants. There are also always dust and bacteria in the air. 

QUESTIONS 

1. Make ;i li-t of ;ill the substances found in the atmosphere, giving the 
amount of cadi thai i- present (whenever given in the text), and 
stating which are compounds and which arc elements. 
_'. Bow do we know thai air i> a mixture of these things and not a com- 
pound of them ( two proofs I '.' 

'■'>. Writ [uations showing the chemical reaction involved when oxygen 

combines with carbon, hydrogen, sulfur, phosphorus, and nitrogen. 
I. Explain in detail why the amounts of carbon dioxide and of oxygen in 
the air remain the same. 

\ means of the data given in this chapter, compute the amounts of 
carbon dioxide, in pounds, over an acre of land. 
•;. What is combust 
7. Describe the element nitrogen. 

s. \\ liy i- the nitrogen of the air of no use to most plants? 
!». What i- nitric acid? What i> it used for? How is it made? 

-plain the process <>f photosynthesis, using a chemical equation. 
11. Why is photosynthesis important? 

■ <■ the chemical and physical characteristics of oxygen. 
lame eighl compounds <>t oxygen mentioned so far in this hook, giving 
both chemical name and common name where possible. 

LABORATORY EXPERIMENTS 

0. To Show the Presence of Carbon Dioxide in the Air.— Almost fill 
two watch glasses with clear linicwater. Immediately cover one of them 
witi ;i glass plate, and leave the other exposed. Altera half hour or more 
examine the surface of each for a cloudy precipitate or sediment. If either 
of them shows the cloudiness, it means thai carbon dioxide has had access 
t<. it. a- carbon dioxide always turn- limewater milky. (See page KM for 
the equation for this reaction.) Why was one watch glass covered and the 

other not Prove 'he pres< n< •«• of ■ arbon dioxide in the breath. 



LABORATORY EXPERIMENTS 27 

7. To Show the Presence of Water Vapor in the Air. — How do the 
following commonly observed facts show that there is water vapor in the 
air: the "steaming" of eye-glasses on coming into a warm room, the 
'"' sweating " of cold water pipes and water pitchers in summer time ? How 
does the water vapor get into the air? What are clouds? How does 
rain form? 

8. To Prepare Nitrogen From the Air. — Set up the apparatus shown in 
figure 2 with a piece of phosphorus the size of a pea on the cork floating on 
the water. (CAUTION: handle phosphorus with forceps!) A glass dish 
or a pan will do for holding the water. Ignite the phosphorus or candle, 
then cover with a quart Mason jar. or with a bell jar, tightly stoppering the 
latter after it is in place. Allow to stand until the burning ceases, and 
all the phosphorus fumes have settled and dissolved in the water. Observe 
the difference in water level inside and outside the jar. What caused this? 
What is the principal gas left in the jar? Thrust a burning splinter into 
it. Explain the result. If all the oxygen had been removed, how much 
would the air inside of the jar have shrunk? What was formed by the 
burning phosphorus ? 

9. The Preparation and Study of Oxygen. — (Two students working 
together. ) Set up the apparatus shown in figure 4. Place in the test tube 
a mixture of 5 g. potassium chlorate, KC10 3 . and 1 g. of manganese dioxide. 
Mn0 2 , which have been ground together in a mortar. Heat slowly along 
the whole length of the tube, holding the burner in the hand. When the 
materials melt and begin to boil, it means that oxygen is being given off. At 
this point regulate the heating so as to just keep the reaction going. Pass 
the gas into the inverted bottles of water. When a bottle is filled, cover its 
mouth with a glass plate, lift from the water, and begin the filling of another 
bottle. When the reaction is over, make the following tests on the bottles 
of gas: 

(a) Thrust a glowing splinter into one of the bottles. How does pure 
oxygen affect the rate of combustion? How would it affect an animal 
breathing it ? What is a pulmotor ? 

( b ) Thrust a glowing piece of charcoal held by tongs into one of the 
bottles and cover it with a glass plate. When the burning has ceased re- 
move the charcoal, put a little water into the bottle and shake vigorously. 
Pour the water into a little clear limewater in a test tube. What was 
formed by the union of the carbon with the oxygen? 

(c) Fill a deflagrating spoon with sulfur, ignite and lower it into a bottle 
of oxygen. When it ceases to burn, remove the spoon, shake the contents 
of the bottle with a little water and then test the water witli litmus paper. 
(See page 142 for the reactions involved.) 

(di Heat a piece of fine bright iron wire red hot and quickly thrust it 
into a bottle of oxygen. What product is formed here 1 

"Write equations showing how carbon, sulfur, iron and magnesium com- 
bine with oxygen. What are oxides? How are they formed? The following 
equation represents the chemical reaction in the preparation of oxygen: 

KCIO3 = KC1 + 3 
potassium potassium oxygen 

chlorate chloride 

The manganese dioxide is added to speed up the reaction : it does not take 
part in it directly. 



CHAPTER IV 

WATER 

Importance. — We saw in the last chapter that one of 
the commonest and most important of the many com- 
pounds of oxygen is water. Until we stop to reflect, we 
do not realize how profoundly water enters into our daily 
Lives. Three-fifths of our body is water; from 75 per cent 
to 90 per cent of all our fresh meats and vegetables is 
water; milk has 87 per cent of water; lettuce and cucum- 
bers as high as 93 per cent; the driest hay is one-tenth 
water; people in the country use from six to eight gallons 
of water per person per day for ordinary household pur- 
poses, and in the city, with street sprinkling, sewerage 
and factories, there is four or five times this amount used. 
The rainfall over most of our average humid states 
amounts to from 30 to 50 inches a year. It takes from 
40t) to 800 pounds of water to produce each pound of 
dry matter in our crops. There is more water surface 
than land on our globe; and in many places the ocean is 
from five to six miles deep. We know that all forms of 
animal and plant life are dependent on water for their 
continued existence. One of the surest ways of killing a 
plant or animal is to keep water away from it. And one 
of the most effective means of preserving meats, fruits 
and vegetables is by drying, since microorganisms cannot 
ferment or spoil them with so little water present. It 
should be pointed oul here that the great majority of 
chemical reactions take place in the presence of water. 
This might be inferred from the statements above, for all 
life processes are series of chemical reactions. In many 
chemical reactions water is not only present, but it also 

28 



ELECTROLYSIS OF WATER 29 

actually enters into the reaction. The conversion of 
starch to sugar by the saliva of the mouth is such a 
reaction; thus: 

C (J H 10 O 5 + H 2 = C,,H 12 6 
starch water sugar 

This kind of reaction will be taken up more fully under 
the chemistry of digestion. Since water is so universally 
important, it is desirable that we take up at this time the 
chemistry of water. 

Composition of Water. — As has been said, water is a 
compound of two elements, hydrogen and oxygen. This 
can be proved in two very interesting ways. The first is 
to decompose water, and prove that the products formed 
are hydrogen and oxygen. The second is to take hydrogen 
and oxygen, cause them to combine, and then note that the 
combination formed is water. 

Electrolysis of Water. — The decomposition of water can 
be brought about in several ways, but the most effective 
and easiest is by means of an electric current. It is done, 
in the apparatus shown in figure 5. It is essentially two 
tubes of water, closed at the top, and connected at the 
bottom; the current passes into one tube, through the 
water to the other tube, then out to the source of the 
current. The water is acidified with a little sulfuric 
acid in order that it may conduct the current more easily. 
The current breaks up the water into the two gases, and, 
due to certain laws of electro-chemistry which we cannot 
go into here, each gas rises in a different tube and collects 
at the top. After considerable gas has been generated, it 
will be noticed that there is twice as much in one tube as 
in the other. Which gas is oxygen and which is hydro- 
gen? From the experiments on oxygen, the student will 
remember that pure oxygen causes such rapid combustion 
that a small glowing coal on the end of a splinter will 
burst into flame when thrust into the oxygen. This test 



WATER 

can now be applied to the gases in the tubes, as the tubes 
are Bupplied with cocks at the top for Letting out the - - 

It will be Pound that the smaller volume of gas is the 
oxygen. The hydrogen can best be tested by making 
>f its inflammability, as hydrogen hums very readily. 
Thus we have proved that water can be decomposed 
into two elements, hydrogen and oxygen. Furthermore, 
the above experiment shows that there are two volumes of 
hydrogen to our of oxygen. The equation for this reaction 
would be as follows : 

Ho = 2H + 
water hydrogen oxygen 

It will he noticed that neither the electric current nor the 
aeid enters into the equation; they are simply part of the 
machinery that does the work. 

Hydrogen. — Before taking up the second proof of the 
composition of water, that is, by combining hydrogen and 
oxygen, we should take a moment to discuss this new 
chemical element that has come to our attention, namely, 
hydrogen. For purposes of study and experiment it can 
repared in several ways. One way, of course, is from 
water by the electric current. A still easier way is by 
allowing some acid, as hydrochloric, to react with some 
metal, as zinc, in an apparatus like the one in figure 11. 
Ajs it> name indicates, hydrochloric acid is a compound of 
hydrogen and chlorine; and when the acid reacts on zinc, 
the zinc displace- the hydrogen. Thus: 

Zn + 2 BC1 = -2 II + Zn< 1. 

rinc hydrochloric acid hydrogen zinc chloride 

The hydrogen is generated in a steady stream from the 
nozzle, and can be collected in bottle- or burned at the 
nozzle. Again, if Bteam is passed over red-hoi iron shav- 

in a tube, the iron combines with the oxygen of the 
■I and liberates the hydrogen. 



COMPOUNDS OF HYDROGEN 



31 



Properties of Hydrogen. — However it is prepared, hydro- 
gen is found to be a colorless, odorless gas, like nitrogen 
and oxygen. Unlike nitrogen, however, it is very active 
chemically ; and unlike oxygen it does 
not support combustion, but burns 
very readily. In fact, burning hydro- 
gen forms one of the hottest flames 
known. In burning, of course, it 
unites with oxygen ; and the so-called 
oxy-hydrogen blow-pipe is a device 
.for producing a small pencil of flame 
for heating small areas of metal for 
welding and cutting ; the limelight in 
stereopticons and theatres is pro- 
duced by a piece of lime heated white 
hot by an oxy-hydrogen flame. 

Hydrogen is the lightest gas 
known, being only one-fifteenth as 
heavy as air. It therefore finds great 
use in the filling of balloons and air- 
ships. This property can be demon- 
strated in the laboratory by blowing 
soap-bubbles with the stream of 
hydrogen from the generator. Be- 
cause of its lightness, there can be 
no hydrogen in our atmosphere, un- 
less it be in the very top layers, 
many miles above the earth. composed into hydrogen gas, 

~ , r tt i mi which occupies the negative 

Compounds Of Hydrogen. There tube, and oxygen gas, which 

. , i a occupies the positive tube. 

are many important compounds of 
hydrogen. For example, all acids contain hydrogen; 
all petroleum products, fats and oils, the carbohydrates, 
ammonia, acetylene, alcohol, are compounds of hydrogen. 
They will be met with further on in their appropriate 
places in the book. 




Fig. 5. — Apparatus for the 
electrolysis of water. An 
electric current is passed 
through the water contained 
in the tubes. The water is de- 



WATER 

Synthesis of Water. — Going' back now to the proposition 
thai hydrogen and oxygen unite to form water, how can 
we prove thai they do! A very simple proof is as follows, 
based on the well-known fact that water vapor condenses 
to a liquid on cold surfaces: if a test tube or beaker full 
of cold water, bul perfectly dry on the outside, is held a 
half inch or so above a Maine of burning hydrogen, in a 
moment the sides of the tube will be covered with a mist 
of line water drops. This water originated in the jet of 
burning hydrogen, and on striking the cold surface con- 
densed to a liquid. The same proof is often furnished 
when a tub of cold water is put over a gas or kerosene 
(lame; the bottom and sides of the tub "sweat" profusely 
until the tub becomes too warm to condense the water 
vapor. These last cases also show that hydrogen is pres- 
ent in considerable quantities in both coal gas and kero- 
sene; in the former it is present as the free element, and 
in the latter in a compound. 

From the above experiments and observations we can 
draw two conclusions: First, that when hydrogen gas 
burns, it forms water; second, that when a compound of 
hydrogen burns, the hydrogen part of the compound forms 
water. The chemical equation involved is as follows: 

2 11 + () = H,0 

hydrogen oxygen hydrogen oxide (water) 

Hydrogen Peroxide.— It has been said above that when 
hydrogen and oxygen combine, it is in the ratio of 2 to 1 
by volume. This is true in ordinary burning of hydrogen. 
Under special conditions, however, these two elements can 
be made to unite in equal parts, that is, two volumes 
of each : 

•-Ml + 20 = 11,(1. 

hydrogen oxygen hydrogen peroxide 

This hydrogen peroxide is the well-known disinfectant 
known also as "peroxide" and "dioxygen." It is also 



IMPURITIES IN WATER 33 

a bleaching agent. It owes both its bleaching and germi- 
cidal effects to the fact that the extra oxygen atom is easily 
broken off, and this atom of oxygen oxidizes away colors 
and kills germs. Only water is left behind; thus : 

h^a = HoO + o 

hydrogen peroxide hydrogen oxide oxygen 

Water as a Solvent. — If water is simply the oxide of 
hydrogen, the question now arises, how can we have good 
water and bad water ? By good and bad one usually means 
good or bad for a certain purpose ; a water may be good 
for drinking, but bad for laundering. We also have soft 
and hard waters, mineral and carbonated waters, and 
others. As a matter of fact, water itself is the same the 
world over, just the same as any chemical compound 
always has exactly the same composition. But water has 
a remarkable capacity for dissolving and absorbing other 
substances. We know that we can dissolve large quanti- 
ties of salt in water to form a brine ; that sugar will readily 
dissolve in water to form syrup ; that most medicines are 
taken in water ; that water dissolves soap, also the dirt and 
stains on clothing. Many minerals dissolve in water; in 
fact, plants get all their mineral food from the soil by 
means of the soil water passing up through the roots and 
stems. In short, water has been called "the universal 
solvent, ' ' since practically everything will go into solution 
in water in some degree. Glass, sand, silver, porcelain, 
will all dissolve in amounts sufficient to be detected by 
chemical means. 

Impurities in Water. — No wonder, then, that water is so 
often impure; it is practically never free from some im- 
purities. As rain falls through the air, it dissolves the 
nitric acid and ammonia formed by the lightning dis- 
charges ; it takes up sulfur fumes, thrown out from smoke 
stacks ; dust and bacteria are brought along to earth, so 

3 



WATER 

• 

that oven raiii-v ntains various foreign substances. 

r rain falling after an hour of heavy 

rail. g, is • from impurities. As the water seeps 

soil ii absorbs g] t number of minerals, 

g nic matter, particles of dirt, bacteria, gases, etc.: 
usual appearance and taste of our river waters. 
If ti. - ps through layers of sand and rock, most 

of ti. - I particles and bacteria are removed from it; 
hence well water and spring water are usually clear. 
But this - ge through rocks does not remove mineral 
matter that - - lution: hence well and spring waters 
may. and usually do, contain considerable mineral matter, 
•ially lime and magnesium compounds. In this same 
way water that falls onto soil contaminated with manure, 
g animal and vegetable matter, etc., becomes con- 
taminated: and many times wells are situated down hill 
from such places, and the contaminated water enters the 
Is disease germs to everyone using it. 
D has a bad smell and taste, and is yellow- 
use of the organic material in it. 
Hard Water. — The commonest impurities in water are 
conr - >f calcium and of magnesium, principally the 

carl- • a and sulfate-. Water containing these sub- 
staifc - - ailed "hard water." These salts get into the 
• r when it flows through limestone formations. It is 
drinking, but when used for washing 
purposes the lime and magnesia combine with the soap 
si ky curd, that is very difficult to remove 
- or tabs. There are several ways of 
sc minerals or "softening" the water; but 
si y involved would be understood with diffi- 
culty at this .it will be taken up in Chapter VIII. 
Purification of Water. — Tib' various impurities in water 
nientrjr, according to the methods 
g them, a- t'<>U<>- - 



PURIFICATION OF WATER 



35 



1. Solid particles in suspension. 

2. Solids in solution. 

3. Gases. 

4. Bacteria. 

A discussion of each of these kinds of substances and 




HM 





Fig. 6. — View in a water filtration plant that has a capacity of 3,000,000 gallons a day. 
The water filters by gravity through beds of fine sand 35 to 40 inches deep. This removes all 
suspended matter, including any sediment produced by the chemical treatment of the water. 

the ways of removing them from water will now be 
taken up. 

1. By solid particles in suspension is meant such things 
as fine sand and clay, pieces of plant material, and 
other substances. They make the water cloudy, and the 
particles can often be seen by the naked eye. These sub- 
stances are removed by a process called filtration. In the 
laboratory this is usually done by folding a special kind 
of paper, similar to blotting paper, so that it will lit the 
inside of a funnel, and then pouring the muddy water into 
the paper. The water can pass through the fine pores of 



WATER 

the paper, lmt the particles of dirt cannot; they are re- 
tained in the paper and the clear water flows out of the 
funnel. In the purification of river and lake waters for 
use in cities, this Bame principle is utilized on an enormous 
Bcale ( Pig. 6). Enstead of filter paper, beds of fine sand 
from 25 to 40 inches deep and covering many square yards 




I i'. .. Automatic machines for feeding chemicals into the water in a water purification 

plant. Lime is added for softening, alum to coagulate the organic matter, and hypochlorite 

of lime to kill bacteria, 

or even acres are used as the filtering medium. Tile 
drains at the hoi torn of the beds carry off the clear water. 
In mosl cases the water is treated chemically with alum, 
in order 1<> coagulate the coloring matter and other organic 
impurities, and these are then left on the sand, together 
with the dirt (Pig. 7). Water softeners are sometimes 
added ;it the same time. In this way very good water for 



PURIFICATION OF WATER 



37 



millions of people is obtained even from snch rivers as 
the Mississippi, the Seine, and the Thames. Brick filters 
are often installed in household rain-water cisterns to 
remove dirt, 

2. When solids are in solution in water the particles 
of the solid cannot be seen; the water is perfectly clear. 
Examples of this class would be sugar, salt, lye, the lime 
in hard water, the alkali in " alkali water." It will be 
readily agreed that filtration would not remove any of 




Fig. 8. — Apparatus for the distillation of water. Water is boiled in the flask at the left, 

and the vapors pass into the long water-jacketed tube, where they condense to a liquid and 

flow into the receiver at the right. 

such substances. Neither can many of them be removed 
by chemical means. Hence, another process is employed, 
called distillation. A simple glass laboratory distillation 
apparatus is shown in figure 8. The liquid to be distilled, 
water, for example, is placed in the flask at the left and 
heated to boiling. The steam can escape only through 
the side tube which leads into the condenser. This is a 
double-walled tube, the space between the walls being 
filled with cold running water. As the steam enters the 
inner tube it comes in contact with the cold walls, and 



88 WATER 

sed into water, which flows out into the receiver 
at the right DistQlati s - iply the of a 

r bad: into a liquid!. 
Thus anything which can I 1 can be distilled. 

It can lily seen that if water containing solids in 

solution, Boch - - It, sugar, or alkali, be put into such 
an apparatus and distilled, the solids will be left behind 
in the distilling flask; the distilled water will be entirely 
>m them. Solid particles in suspension, as dis- 
— ed in paragraph 1. p. \ old, of - . also be 

left behind. 

Importance of Distillation. — Distillation is of very great 
industrial importance. By this «ss alcohol is removed 
from fermented liquor, and we thus _ * ur distilled 

■ _ 9 nd «>ur pure alcohol. Perfumes are rem 

from flowers by distillation; the nicotine is distilled from 

ste tobacco and used as an insect poison: turpentine, 

many medicinal oils, carbolic acid, tar, ether, chloroform, 

;11 obtained by this method. But no doubt the largest 

distillation industry in the world is that of petroleum. 

:i the crude oil is pumped from the ground, it is a 

mixture of d 3 of different substances, each of which 

rizefl t a different temperature. When the oil is 

placed in a distilling apparatus and heated, the substances 

of Lowest 1 "oiling point vaporize and condense first, those 

of highest boiling point last. In this way succ ssrv :rac- 

Istilled over, and we have gasolene, naphtha. 

. paraffine, lubricating oils, and many 

others. Millions of barrels of oil are distilled yearly in 

this country. Long rows of stills, each holding as high as 

operated at one time. They are fed from 

the <>il fields by pi; - that in many a - are over 

I a long. 

Isfi Lve in water; air - able 

arbon dioxide to a still greater extent, and the 



IMPORTANCE OF DISTILLATION 39 

gases formed in decomposing vegetable and animal matter 
in sewerage, soil, manure, etc., to an extent sufficient to 
make them very disagreeable to smell and taste in many 
cases. Their removal, however, is very simple, and can 
be illustrated by a simple experiment. Some odorous gas, 
such as hydrogen sulfide or ammonia, is dissolved in a 
beaker of water and the latter boiled. A few minutes of 
boiling will entirely remove the odor of the dissolved gas. 




Fig. 9. — Apparatus for demonstrating the presence of water in fresh plant tissue. 

This is because the gas is not soluble in boiling water. 
When a tub of water begins to warm up on a stove, bubbles 
of gas appear on the bottom and sides long before the 
water begins to boil; these bubbles are the air that was 
dissolved in the water. This can be demonstrated by 
placing a minnow in some boiled and cooled water; it will 
soon suffocate because of lack of oxygen. (See experi- 
ment 15.) Thus, gaseous impurities can be removed 
by boiling. Although distillation also involves boiling, 
the gases will redissolve in the cooled condensed vapors, 



46 



WATER 



and tlu 1 distillation will not succeed in removing- them. 
4. Bacti ria are minute one-celled plants that are found 
practically everywhere in countless myriads. Many of 
them are harmless; many are very beneficial; but some 
of them are the causes of our most serious diseases. A 
few disease-producing organisms occur hi polluted water, 
and in this way find their way into the bodies of man 
rnd animals. Typhoid, cholera, and dysentery are among 

o u r most dreaded 
water-borne diseases. 
Hence, it is very often 
important that w e 
have means of killing 
or getting rid of them. 
Fortunately, heat is 
our most effective dis- 
infectant, and can be 
used on a small scale in 
the home f o r both 
w a t e r and milk. It 
wonldbefar too costly, 
however, for purifying 
the water for a city. 
Since a bacterium is a solid plant body, although a very 
small one it belongs to the class of substances discussed 
in paragraph 1. and can be removed by filtration, provided 
the pores of the filter bod arc lino enough to retain them. 
This method is universally used in the big filtration plants. 
Chemicals, of course, such a- corrosive sublimate, car- 
bolic acid, hydrogen peroxide, formaldehyde, and alcohol, 
are commonly u<^\ for killing bacteria in wounds, on im- 
plements and clothing, in rooms, etc., but obviously can- 
not be put int.. drinking water for that purpose. There 
are, however; two ?ery effective germicides, which can be 
used with perfect safety in city water supplies, because 







in. — Homo-made apparatus for the electrolysis 
Of water. 



IMPORTANCE OF DISTILLATION 



41 



the active agent is completely used up in the process. 
These two reagents are hypochlorite of lime and chlorine, 
The element chlorine is really the active constituent in 
both of them. It requires only a few pounds of either of 
these substances to sterilize a million gallons of water. 
The chemical reaction involved is essentially as follows : 



2C1 + h 2 o 

chlorine water 



2HC1 
hydrochloric acid 




oxygen 



Thus the chlorine does not kill the bacteria directly; it 




Fig. 11. — Apparatus for the preparation of hydrogen 



liberates an atom of oxygen from the water and this does 
the work. Hypochlorite of lime is ordinary bleaching 
powder; in this case its action is the same, the oxygen 
formed serving to oxidize away the color. In swimming 
pools, where not much water is supposed to be taken into 
the body, copper sulfate, blue vitriol, is often used 
as a disinfectant. 

The above cases cover all the ordinary kinds of im- 
purities that are dealt with in water. There are many 
special industrial uses for water where other problems of 
purification are met with; for example, in laundries, 
brev r eries, chemical works, and steam boilers. 



t2 WATER 

QUESTIONS 

1. Describe two different met - :• roving that water is composed of 

■ 

mpute a; : you take into your body in 

I and drink every year. 
.?. Describe - giving both its physical and chemical proper! 

4. What • _ sea - ydrogen g - 

ft, T< !1 wiiv rain water is really distilled water. What impurities may rain 

r ry ? 
o. Describe tin that water follows before it arrives in our well for 

drinking, and state the impurities it may have acquired. 
7. What i- bard trsi 

| repare good water for laundering from a mud puddle? 
How \>r< | _ irinking water from it? 

'.'. What is riltrat: 

10. What is distillation 1 Name ten substances that are manufactured by a 

filiation. 

11. What ar*» bacterial How can they be harmful? What three general 

methods are there for removing them from water or killing them? 

12. How tan you prove that air dissolves in water? 

LABORATORY EXPERIMENTS 

io. To Prove the Presence of Water in Fresh Plant Tissues. — Set up 
the appara- - - n in figure 9. filling the test tube with lettuce or cab- 
bage - or apple. Heat the tube very gently with a 
ime. avoiding scorching of the material. What liquid forms in the 
ste it. and let some of it drip into some blue vitriol that has 
been heated until it is w What does this prove? The 
has been removed from the plant tissue by distillation (p. 37 » . What 
-tilled wa- 
il. The Electrolysis of Water. — To be done by instructor, i Fill 
the apparatus with 5 per cent sulfuric acid (since water alone does not con- 
duct electricity sufficiently well | . Be sure that the tubes are completely 
filled. Any direct current will do which gives 4 to _ ta Four 
dry hatter - ry well, although slowly. Xote the relative volume of 
-med in the tubes. Allow the gas of smaller volume to escape through 
the si _ ing splinter. Explain the result. Ignite the gas 
from the other tube with a match. Does this test apply to hydrogen only, or 
would Kime otl erg - - :m? What does this experiment prove concerning 
- ■ 
If regular a; •: - For the electrolysis of water is not obtainable, the 
appar itas t m in figure 10 can be set up. The electrodes can be of cop- 
: latinum is preferable. 
12. The Preparation and Study of Hydrogen. — To be done by 

vn in figure 11. Place about 10 g. 

of flake zinc or iron nails in the fla^sk. place the stopper in firmly, and 

pour dilute hydrochloric or sulfuric acid down the funnel. Allow the gas 

- ape into the air for at least fire minutes by the dock. 

res all air out of the flask, replenishing the acid if the generation 

hen pin a stout towel around the generator. These 

« mutt be observed in order to prevent explosions. The hydrogen 



LABORATORY EXPERIMENTS 43 

may now be collected in wide-mouth (never in narrow-mouth; why?) 
bottles. Make tests on the gas as follows: 

(a) Test the inflammability of the gas in one of the bottles. 

(b) Light the hydrogen as it issues from the generator. Hold a test tube 
or beaker filled with cold water just above the hydrogen flame for a few 
seconds. What forms on the outside? What is its source? Write an equa- 
tion showing the reaction when hydrogen burns. What is the oxy-hydrogen 
torch and for what is it used? 

(c) Holding a bottle of hydrogen upside down, thrust a burning 
splinter into the bottle clear to the bottom. Does hydrogen support com- 
bustion? Would a jet of oxygen burn in a room full of hydrogen, the 
same as a jet of hydrogen burns in a room full of oxygen? Why? 

(d) Test the lightness of hydrogen by holding the tube from the gen- 
erator in a bottle right side up, and a bottle upside down, and then testing 
each bottle for hydrogen with a match. Is hydrogen lighter or heavier 
than air? What practical use is made of this fact? 

13. To Show Various Degrees of Solubility in Water. — Into separate 
test tubes containing 5 c.c. of distilled water add 5 g. of CaS0 4 , CaC0 3 , and 
CaClc, respectively. With the thumb over the test tube shake each of them 
thoroughly for at least a minute. Filter each solution. The filtrates are 
saturated solutions of the various salts. Place five drops of each on watch 
crystals and evaporate to dryness. Compare the amount of residue on each. 

14. To Demonstrate the Solids Dissolved in Various Waters. — Fill 
separate watch glasses with (a) distilled water, (b) rain water, (c) hard 
water from a well or city main, (d) river or other muddy water, and (e) 
the same water as in (d) but filtered through double filter paper. Evaporate 
to dryness, and compare the amounts of residue. What is the source of the 
residue in (b) ? Put a few drops of dilute hydrochloric acid on the residue 
in ( c ) , and also on a little powdered limestone. If the residue in ( c ) 
effervesces, what does this signify as to its composition? What is the dif- 
ference between the kinds of substances in the residues of (d) and (e) ? 

15. To Show the Presence of Dissolved Air in Water. — (a) Warm 
some tap-water in a beaker. What are the bubbles of gas which form on 
the sides and bottom ? How do you know they are not bubbles of steam ? 

(b) If two minnows or gold fish are obtainable, test the solvent power 
of water for air as follows: Boil a quart of water for several minutes, then 
completely fill a large beaker with it while still hot. Cover with a glass 
plate and allow to cool. Meanwhile fill another beaker with water that has 
been aerated by being poured violently from one dish to another. Cover this 
also with a glass plate. Now place a minnow in each beaker and watch 
their behavior for some time. Which first shows signs of an insufficient sup- 
ply of air ? What did the boiling do to the water ? 

16. To Show the Process of Distillation. — ( To be done by instructor. ) 
Distill some muddy water, and then some vinegar. Note the appearance, 
taste, and odor of the distillate. From what sorts of impurities can water 
be freed by distillation ? What kinds of substances can be distilled ? 



CHAPTER V 

COMBUSTION AXD FUELS 

studied briefly the various gases found 
in the atmospln seen that the nitrogen is of 

little chemical importance, but that compounds of nitrogen 
arc me importance in plant and animal life and 

in certain industri< - ; that the carbon dioxide of the air, 
although present in very small amounts, is the sole source 
of carb«»n for all plants, and that tons of carbon are taken 
from the air by each acre of crops; we have seen that 
ae-fifth of the air, and supports all 
combustion on the earth. We have only briefly discuss 
the immense magnitude and importance of this process 
>mbustion: and since it is a far bigger subject than 
our difi 58 dd indicate, we will take it up more in 

Combustion, ; g said, is rapid union with oxygen, 

mpanied by the production of heat. Therefore, com- 

e called oxidation. There are a few 

exceptions to this where combustion does not involve oxy- 

tbe considered here. Practically all 

;r ordinary combustion is the burning of fuel in one 

of two places, either in engines to give energy for running 

machinery, or in animal bodies to keep them warm and 

[*ive them energy to do work. Therefore the chemical 

union i^ oxygeu with fuel supplies all the heat and 

mechanical • gy of the worl< pt the little that we 

from wind, falling water, and the sun. That the 

bod is really the original source of our fuel will be - 

in a later chapter. 

A study "i' combustion, then, is a study of oxygen and 

M 



FLAMES 45 

of fuel. We have already considered the chemical charac- 
teristics of oxygen, and we have mentioned that carbon is 
the most important fuel element. They unite to form 
carbon dioxide: 

C + 20 = C0 2 

carbon oxygen carbon dioxide 

Besides carbon, hydrogen is also a very important fuel 
element, either free or combined with carbon : 

2 H + = H 2 
hydrogen oxygen water 

Let us keep in mind from the beginning that carbon diox- 
ide and water are always formed when carbon and 
hydrogen burn, whether these elements exist free or in 
compounds. An interesting fact that should be noted 
here is that whereas both carbon and hydrogen as elements 
may be burned in furnaces and engines, they can be 
burned only as compounds in animal bodies. 

Kindling Temperature. — It is a commonly observed fact 
that before a substance will burn it must be heated to a 
certain temperature. We find it impossible to fire coal 
with a match; hence we use the match to light a piece of 
paper, the paper lights some wood, and the wood starts 
the coal to burning. The temperature at which the com- 
bustion of a substance will commence is called the kindling 
temperature. The kindling temperature of the paper is 
lower than that of the wood, and this lower than that of 
the coal. Iron does not ordinarily burn ; but if it is heated 
very hot it oxidizes on the surface and sniffs off. The 
kindling temperatures of gases are usually lower than 
those of solids. 

Flames. — When a gas burns, a flame is always pro- 
duced; hence we can define a flame as being the combustion 
of a gas. Also we can say that wherever there is a flame 
there is a burning gas. This may seem contradictory at 



Ih 



COMBUSTION AND FUELS 



first, since wo have all seen both liquids and solids burn 
with flames. The explanation of this, however, is that 
when kerosene burns, for example, it is the vapor of the 
kerosene that is burning and producing the flame. The 
sanif is true of alcohol, gasolene, or other liquid fuel; they 

are first vaporized by 
the temperature of the 
air or the match which 
lights them, and then the 
vapor burns. When a 
kerosene stove is " gen- 
erated/' it means that 
some of the iron parts 
must first be heated by a 
little kerosene burning 
in a special cup, so that 
when the regular burner 
is lighted, the heated 
iron will vaporize the 
kerosene as it flows into 
the burner, and thus 
produce a vapor for 
combustion. 

The Burning of Wood 

Structure distillation of wood. Pieces of hard wood and Ol Uoal. 111 LJie CaSeOI 

are put into the teat-tube and then roasted. The . „ , , 

gaseous product* that are driven off from the wood a piece 01 WOOd DlimiHg 

l from the vent, whore they can be burned. . , a . . . 

After no further gee W evolved, charcoal remains Willi a flame, the Origlll 
in the tube. Commercially, the gaseous substances « . , . . .. 

,n n.t burned, but are made to yield wood alcohol, 01 the gaS IS not OUlte SO 
acetone, and acetic acid. , _ , , 

clear. It can be shown, 
however, as follows: a few pieces of wood are put into a 
test tube, the month of the test tube is fitted with a cork 
containing a small glass tube, and the wood in the test tube 
is gradually heated with a burner (Fig. 12). Soon the 
wood begins to blacken, thou to give off vapors and fumes. 
[fa lighted match is applied to the gases issuing from the 




THE BURNING OF WOOD AND OF COAL 47 

mouth of the test tube, they will burn readily, and will con- 
tinue to do so for some time. When they cease burning, and 
the contents of the tube are examined, they will be found 
to consist of pieces of charcoal. If these are placed on an 
asbestos or iron plate, and fired by the burner, they will 
burn with a glow just like charcoal, and with practically 
no flame. We can now see that the burning of a splinter 
of wood proceeds somewhat as follows : The flame of the 
match heats up the end of the stick until some gases are 
driven off; these catch on fire and burn readily now with- 
out the match. The heat from the burning gas liberates 
more and more gas from the wood, and we have a flame 
as long as any gaseous substances remain in the piece of 
wood. Then the flame dies out and the piece of wood burns 
simply with a glow. It is now the charcoal, or carbon, 
part of the wood that is burning; and when this is con- 
sumed, the combustion ceases, and nothing but the ash 
remains. The same process takes place when coal burns ; 
first the gas burns with a flame, then the carbon part burns 
without flame. And the big difference between soft and 
hard coal is that the former has considerable gaseous 
material liberated when it is fired, and burns with a flame, 
while hard coal is practically all carbon and burns with 
very little flame. 

The gaseous and solid constituents of wood and coal 
are of great industrial value. Charcoal has been pro- 
duced for centuries. Wood is stacked in a loose pile and 
covered with earth and sod, leaving a few vents for air 
around the bottom and one in the middle at the top. The 
amount of air is so controlled that the gases in the wood 
can be liberated and burned, but that the charcoal will be 
left behind unburned. The modern practice is to roast the 
wood in huge retorts, and instead of burning the escaping 
gases to separate from them many valuable products, such 
as wood alcohol, acetone, and acetic acid (Fig. 13). The 



- 



'MBUSTIOX AND FUELS 




"5 "*■• 

_ T. 



IE "q 



— x 

- - 



g-a 



COAL GAS 



49 



uses of charcoal are discussed in the next chapter. The 
above process is a certain kind of distillation called de- 
structive distillation. It is called destructive, because the 
composition of the wood is entirely altered; profound 
chemical changes take place, and substances are formed 
which never existed in the original wood. 

Coal Gas. — The destructive distillation of coal is one of 
our greatest chemical industries. The gas produced, com- 



MaMteatttoto 





w/m 



Fig. 14. — Diagrammatic cross-section of a coal-gas oven. Soft coal is charged into the chamber 

B, and roasted by the hot fire in A. The gaseous matter driven from the coal passes out at C 

into a long series of machines which remove the tar, the sultur compounds, the ammonia, 

and other impurities. The purified gas is then pumped into the city mains. 

monly called illuminating or coal gas, supplies most of our 
cities with fuel for domestic purposes. The coal (always 
soft coal, because it contains the most gaseous material) 
is stoked into huge ovens and roasted, air being kept away 
from it (Fig. 14). The gas which is driven off contains 
many valuable impurities, such as tar, ammonia, and ben- 
zol, and they are extracted before the gas is turned into the 
4 



50 < OMB1 STION AND VIVA- 

city mains. Prom the tar are extracted many compounds 
Important agriculturally, such as cresols for stock dips, 
creosote for preserving fence posts, carbolic acid, naph- 
thalene Tor moth-balls, tar and pitch for roofing and road 
materials, toluol (indirectly used in explosives), and 
ammonia tor fertilizers. 

Tlu 4 solid material left behind in the ovens is called 
coke. It consists almost entirely of carbon, together with 
the ash of the coal. It is used for burning in furnaces to 
some extent, but its greatest use is in the smelting of iron 
and other metallic ores. 

It must not be inferred by the student that when wood 
and coal are destructively distilled, and carbonaceous 
material like charcoal and coke are left behind,//// of the 
carbon of the wood or coal is thus left ; most of the gaseous 
compounds also contain carbon, the principal one being 
methane, CH 4 . Hydrogen gas is the other main con- 
stituent of coal gas. 

For convenience, fuels are divided into three classes, 
solid, liquid, and gaseous. 

Coal. — The principal solid furls are coal, wood, and 
charcoal, coal being by far the most important industrially 
( Kilt. 15). The formation of coal in the earth is a very 
interesting geological story, although it is still imperfectly 
known. At a time when the climate of the earth was very 
much warmer and more humid than it is now, when 
tropical jungles and swamps were prevalent over most of 
tin- United State-, vegetation grew rapidly, died, and 
decayed rapidly. Tree ferns were one of the principal 
swamp plants of the time; as they fell they decayed in 
the Bwamps under water, were buried by other falling 
trees, continued to decay and to be buried deeper and 
deeper, were subjected thus to decomposition under hot 
BWampa, and finally in the course of time had formed coal. 



PEAT 



51 



Depending on how far this decomposition had proceeded, 
we have various grades and kinds of coal, from lignite, one 
of the first stages, through soft coal to hard coal, which is 
the highest stage of this decomposition. 




Fig. 15. — Battery of mechanical stokers. The coal flows down the chutes from bins and 

is fed into the grates in an even, steady stream, resulting in much more effective combustion 

than when it is hand-fired. 

Peat. — Coal is probably not being formed anywhere 
on earth at the present time; the proper climatic con- 
ditions and kinds of plants are no longer present. But 
we do have decay of vegetable matter along such similar 
lines that we believe it is comparable to the first stages of 
coal formation. Thus in our peat bogs, the grasses and 



52 MBD8TION AND FUI 

ssefi are dying down e , i>eing buried m 

new growth, a - ter. The top 

at hav. s that of the 

ts; the lower . s nearly that of 

1 1 '-nee we c a in a general way that coal has 




• — The analysis of coal. A carefully weighed sample of coal is placed in the crucibles. 
These are placed in the small furnace and roasted with the covers on to determine the amount 
of volatile gases. They are then ignited with the covers off, to determine the amount of 
carbon and of ash. (Copyright, Underwood and Underwood, N. Y 

d through the following stages: lants, dead 

plant . hard o 

This proa 98 Is showi i [so in the chemical analysis of 

An analysis usually shows the 
amoi d which is driven off by r 

• hind 



ALCOHOL 



53 



as coke, and the amount of ash. The following table pre- 
sents the analyses of wood, peat, and coal: 

Table III 

Composition of Various Solid Fuels 





Gas 
per cent 


Uncom- 

bined 

carbon 

per cent 


Ash 
per cent 


Wood 


50-70 

40-60 

20-35 

5-10 


20-35 
20-40 
50-75 
80-90 


3- 8 


Peat 


10-30 


Soft Coal 


5-15 


Hard Coal 


5-10 







It will be seen that as we go from wood through peat, 
to soft and to hard coal, there is a rapid increase in the 
amount of carbon, and a decrease in the volatile gases. 




Fig. 17. — A California oil field. In order to speed up the production from a given claim, a 

great many wells are driven into the same oil beds. This is a waste of capital, however, 

since the beds are more quickly exhausted, and then the derricks have to be moved to a 

new location. (Courtesy of U. S. Geological Survey.) 

And this is really the sum and substance of the chemistry 
of coal formation. 

Alcohol. — Our common liquid fuels are practically 
limited to alcohol and to the petroleum products. Alcohol 



•MBUSTION AND FUELS 

g reduced when yeast ferments sugar. The alcohol is 
distilled off and concentrated, and used for many pur- 
- 8, including burning as a fuel in lamps. However, in 
this country it cannot be produced cheaply enough to be 
very extensively in this way. Starch of potatoes and 
- a hanged to sngar and then to alcohol. 
Petroleum. — Petroleum is found in enormous quantities 
in various parts of the world, especially in the United 
States, Russia, Roumania, and Mexico. The world's pro- 
duction of crude oil is about 460,000,000 barrels a year. 
Ifoh- are drilled down into the oil beds and the oil pumped 
up like water ( Figs. 17-18). In some cases the oil is under 
such tremendous pressure that it spouts out of the drill 
hole to a considerable height. This kind of well is called 
pusher. " If it accidentally takes lire, it is very difficult 
to extinguish. The oil is often a black, disagreeable smel- 
ling liquid. A- discu — I in the last chapter, it is sepa- 
ral constituents by distillation. Gasolene 
finds most of its usefulness as the fuel in motors, while 
►stly used in stoves or under boilers for 
m production. 

Fuel Gases.— The § fuels that are produced and 

used to-day are numerous. The leading ones, of course, 

are the i s discussed above, and natural gas. The 

r occurs in huge pockets beneath the ground in the 

<»il i' g - >f the world. It consists mostly of methane, 

CH 4 . It is ready for burning without any purification, 

ensively used in the smelting industries, 

s, and for household use in cities. In small 

towns, when torj for making coal gas would not pay, 

LS made, by passing steam over red- 
»ke. The product formed Is a mixture of two gases, 
carbon monoxide and hydrogen : 

d monoxide hydi 



FUEL GASES 



55 




Fig. 18.— An oil tank on fire. Such fires are most spectacular, since there are huge quanti- 
ties of oil involved, and since the poor access of air causes the production of enormous 
masses of black smoke. (Courtesy of U. S. Geological Survey.) 



56 COMB! B . kND FUI 

This carbon monoxide sarbon di . it should be 

noted. It will be taken up in the next chapter. Acetylene 
gas for illuminating purposes. It is 
produced when calcium carbide is acted upon by water: 

- 2H4>= I .II. - l 
calcium carbide water acetylene slaked lime 

•dene generators are commonly installed in farm 
- 3. The gas _ - rilliant white light, if it is pro- 
vided with a proper burner, which admits the right 
amount of air for comp- nbustion. This gas is very 

much used in bicycle and automobile lamps. It is also 
g I like hydrogen in the oxy-acetylene torch for welding 
and cutting Bteel ( : Other easeous fuels of less 

importance are also manufactured, but they need not be 
mentioned here. 

Fire Extinguishers. — We have seen that a substance 
will not bum until it has been heated to its kindling tem- 
perature ( - . if a burning substance is cooled 
w its kindling temperature it will cease to burn. This 
principle is the basis of the use of water in f i ihing 
The water thrown on a pi - the 
temperature of the latter down, as the heat of the fires is 
up in driving out the water, and if sufficient water 
d, the lire will be extinguished by the time the 
"it and raised to the kindling temperature. 
j is thi a why w _ ts e slowly in a 
bonfire; the water must be driven out before the wood 
can fo ised to the kindling temperatn 

Another principle utilized in extinguishing firea is 
that, if oxygen (that i>. air) can be excluded from the 
fire, the latter will hav - mbustion is not 

jible without oxygen. The air is excluded in a nun 
of ways. In tie- firs! place, when water i> thrown on a 



FIRE EXTINGUISHERS 



57 




Fig. 19. — The oxy-acetylene torch, used in cutting steel plates in the ship-building industry. 

Oxygen and acetylene are contained in the two tanks under pressure. The two gases mix 

and burn at the nozzle, forming a pencil of extremely hot flame which melts a cut through 

the steel. (Courtesy of Committee on Public Information.) 



58 



( !( )Mlil STION AND FUELS 



blaze, it not only cools down the materials, but the large 
volume of steam produced forces away the air, and thus 

aids in checking the fire. The 
commonest method of excluding 
air from a fire is to throw around 
the base of the fire large volumes 
of some gas that will not burn. 
This is the so-called chemical 
fire extinguisher. The usual gas 
that is used is carbon dioxide. 
We have seen above that this 
gas is formed when carbon 
burns; it is also formed when 
any acid acts on a carbonate, as 
we shall see in the next chapter. 
The apparatus used as shown in 
figure 20 consists of a tank, with 
a hose and nozzle attached. The 
tank is filled with a concentrated 
solution of baking soda (sodium 
bicarbonate); and suspended 
from the top is a bottle of sul- 
furic acid. As long as the two 
are kept separate there is no ac- 
tion ; when the tank is inverted, 
however, the acid comes in con- 
tad with the carbonate solution, 
and carbon dioxide gas is gen- 
erated and flows out of the 
hose, together with the water 
in a fine spray, The stream 
of gas and water is played 
around the base of the fire to exclude the air, and thus 
extinguish the flames. The reaction in the fire extin- 
her is aa follows : 







Fie. 20. — Chemical fire extin- 
guisher. When the machine is 
inverted, :i cup of Bulfuric acid 
is emptied into a reservoir of 
sodium bicarbonate solution. A 
large volume of carbon dioxide i.s 
generated, which issues from the 
ixed with the liquid, and 
i around the base of 

tlie fire. 



LABORATORY EXPERIMENTS 59 

2NaHC0 3 + H 2 S0 4 = Na 2 S0 4 + H 2 + C0 2 

sodium bicarbonate sulfuric acid sodium sulfate water carbon dioxide 

After using, the apparatus has to be cleaned and replen- 
ished. Fire department wagons of cities carry steel cylin- 
ders containing large volumes of carbon dioxide under 
pressure. Simply opening a valve liberates a jet of the 
gas from the hose attached. The throwing of a blanket 
on a burning object stops the fire by excluding the air 
in a similar manner. 

QUESTIONS 

1. What is oxidation? 

2. Why is combustion important? 

3. What are our two most important fuel elements? What product is 

formed by the combustion of each ? 

4. Name fuels that contain : 

(a) Carbon as an -element. 

(b) Hydrogen as an element. 

(c) Carbon and hydrogen as compounds. 

5. What is the kindling temperature of a substance? Explain why coal 

cannot be lighted by a match. 

6. What is a flame? 

7. Describe the different steps involved in the burning of a piece of wood. 

8. Describe how coal is destructively distilled, and name the various 

products obtained from it. 

9. Why is soft coal used for making coal gas instead of hard coal? 

10. Make a list of all the fuels that you know, grouping them as solid, liquid 

and gaseous, and stating after each one whether it contains carbon 
and hydrogen as elements or compounds (get instructor's aid where 
needed ) . 

11. Describe the successive stages in the formation of coal. What has been 

the fundamental chemical change here ? 

12. State the two general principles utilized in extinguishing fires. 

13. How do the " chemical fire extinguishers " work? 

14. Write an equation showing the reaction when acetylene burns. 

LABORATORY EXPERIMENTS 

17. To Prove That Carbon Dioxide Is Produced by the Combustion 
of Food in the Body. — By means of a glass tube, blow the breath for a 
minute or so into some clear limewater in a test tube. From what was 
learned of the chemistry of limewater in experiment 6, explain the results 
of the experiment. In what experiment was it proved that the combination 
of charcoal and oxygen produces carbon dioxide? Is the carbon which 
is burned in the body in the form of an element or of compounds ? 

18. A Study of Flames. — Make a drawing of the Bunsen burner, show- 
ing particularly the air holes at the base and the two principal portions of 
the flame. Where does the gas enter the burner? Where do gas and air first 



iMBUSTION AND FUEL- 

What i> the result - - the air holes": Prove to what the yellow- 

f this Same is due by holding a piece of cold porcelain in the flanie. 
is this luminous flame wasteful of gas for heating purposes but more 
efficient for lighting": Of what <loes the inner cone of the non-luminous 
flame - si Hold one end of a piece of glass tubing in this cone and 
light t _ - sailing from the other end. Then hold the tube just above the 
inner cone. What do these tests prove concerning the progress of combustion 
in the flan ta rtain whether a candle or an alcohol flame has the same 

structure as the Bun-en burner. 

19. The Destructive Distillation of Wood and Coal. — Set up the ap- 
paratus Bhown in figure 12. Fill the test tube with hard-wood sawdust or 
>mall pieces of hard-wood, fix the cork in firmly, and carefully heat the test 
tube until the gases given off will ignite. Continue the heating until no 
further inflammable gas is given off. What are some of the constituents 
of this gasl How were they formed": Examine the residue in the test tube. 
Place it on a wire gauze and ignite it with a burner until it ceases to burn. 
- il burn with much flame or does it glow like charcoal? Of what does 
the final incombustible re>idue consist 1 Repeat the above experiment, using 
al. What is the residue in the test tube called in this case? What 
prod - parated from coal ga? commercially? 



CHAPTER VI 

CARBON 

Occurrence of Carbon. — We have already discussed the 
element carbon to a considerable extent. We have seen 
that it occurs in the atmosphere as carbon dioxide in 
small amounts ; that plants extract large quantities of it 
from the air to build up their bodies ; that coal is princi- 
pally carbon, especially hard coal ; that when plant mate- 
rial is roasted without access of air, charcoal, which is 
practically all carbon, is left behind ; that almost one-half 
of the dry matter of all plant and animal bodies is carbon ; 
that it is the most important of our fuel elements. But 
even these things do not cover the usefulness of carbon ; 
there are many more interesting chemical stories concern- 
ing it, which we will relate in this chapter. 

Although a very common element in our daily life, 
carbon constitutes only one five-hundredth of the weight 
of the earth's crust. It forms more compounds than any 
other element, something like 100,000 of them being known 
at present. In one form (diamond) it is one of our most 
beautiful gems; in another form (soot) it is one of our 
blackest and grimiest of substances. 

Forms of Carbon. — Carbon as an element occurs in three 
forms : diamond, graphite and charcoal. Diamond is 
pure, crystalline carbon; it has a brilliant lustre, and 
breaks up light into many colors. Most diamonds are 
white, while others are tinged with color due to mineral 
impurities. It is the hardest substance known, and hence 
furnishes a valuable means of grinding and cutting other 
hard substances. Broken and badly colored pieces are 
used in glass cutters, rock drills, and grindstones for other 

61 



62 CARBON 

gems. We know that diamond is carbon because it burns 
in oxygen to form nothing- but carbon dioxide. Its origin 
in the earth is not known exactly, but the carbon no doubt 
had an animal or vegetable source; under certain con- 
ditions of heat and pressure charcoal was formed, and this 
underwent still further effects of heat and pressure, be- 
came Liquid carbon, and then crystallized into diamonds. 
We believe this to be the process because it has been 
imitated artificially. The brilliant French chemist, Henri 
Moissan, not many years ago, dissolved pure charcoal in 
molten iron, in an electric furnace, then plunged the 
mass of white-hot iron into water. The tremendous pres- 
sure of the contracting and cooling iron resulted in the 
formation of a great many very small crystalline dia- 
monds, which were found imbedded all through the iron. 
These crystals are just as hard and as brilliant as the 
natural gems, but as yet they cannot be made large enough 
ior jewelry purposes. 

Graphite is also crystalline carbon, although it has a 
different crystal form from that of diamond; is black or 
grayish black, and very soft and greasy to the touch. 
These latter qualities make it a valuable lubricant, espe- 
cially when ground in oil. Another common use of 
graphite is in lead pencils. Here it is mixed with clay; 
the more clay that is used the harder the pencil. It is also 
incorporated into paints for iron parts. Although 
graphite occurs in fairly large quantities in Ceylon, 
Siberia and the United States, a great deal of it is made 
artificially, by fusing coke in an electric furnace, shown 
in figure 21 . 

By the term <h<n<<><il here we mean any form of carbon 
other than diamond and graphite. We have seen in the 
lasl chapter that charcoal is produced when the gaseous 
materials are driven out of wood; that coke is a form of 
charcoal produced in a similar way from coal, and that 



FORMS OF CARBON 



63 



coal, especially hard coal, is mostly carbon, and hence we 
can think of it as being the charcoal produced in nature. 
Both our charcoal from wood and our coke from coal 
are light, porous substances, but we can imagine that if 
they were subjected to great grinding and pressure in the 
earth, they would come out of it in hard, compact form 
like coal. In other words, we can go to nature and find 




Fig. 21. — An electric furnace for making graphite. This is the only kind of furnace which 
develops a sufficiently high temperature for the formation of the graphite form of carbon. 

all the stages of carbonaceous decomposition; starting 
with living plants, then dead plants, then peat, lignite, 
soft coal, hard coal, graphite, and end up with absolutely 
pure, crystalline carbon in the form of diamond. To be 
sure, we do not know that exactly the same process was 
involved here from start to finish; but the series at least 
illustrates that nature is provided with chemical processes 
for obtaining pure carbon from plant and animal tissues. 



04 



CARBON 



Iii all probability plant and animal tissues were subjected 
to a BOmewhal different treatment in other parts of the 
earth and at different times, and resulted in our beds of 
petroleum and pockets of natural gas. We shall have oc- 
casion to mention other deposits of minerals which prob- 
ably had an origin in plant 
or animal materials, such 
as the nitrate beds of Chile, 
the phosphate rock of Flor- 
ida, and the huge deposits 
of limestone all over the 
world. These facts indi- 
cate the close connection 
between the inorganic or 
mineral world and the or- 
ganic or living world. 

Kinds of Charcoa 1. — 
( harcoal is given a special 
name, according to its 
source. Thus, the charcoal 
from kerosene is called 
lampblack; from bones, 
bone-black; from blood and 
other slaughter house resi- 
dues, a n i m a I charcoal; 
from wood, wood charcoal. 
From whatever source, 
charcoal is a jet-black, light, porous, soft, easily powdered 
Bubstance, very resistant to the action of chemicals. Its 
most remarkable property is that of absorbing gases and 
coloring matter. A piece of fresh charcoal will absorb 
eighty times it- volume of ammonia or other gas (Fig. 22). 
It is commonly thrown into vaults, cisterns, and refuse 
piles to absorb offensive odors. When powdered char- 
coal Is shaken up with colored Liquids and filtered, a great 




22 — Apparatus showing the power of 
charcoal t<« absorb gase9. The test tube is 
tilled with ammonia, hydrogen sulfide, or 
other jca.*, and then >et down over a piece of 
fresh charcoal floating on the mercury. The 
eharooal absorbs the gas, creating a partial 
vacuum, drawing mercury up into the tube. 



CARBON DIOXIDE 65 

deal of the coloring matter is removed. Great quantities 
of charcoal are used in this way in purifying cane and 
beet juices in sugar manufacture. 

Battery Carbons. — When charcoal is powdered and 
pressed into solid bars it is given the trade name of car- 
bon. As such it is used in many electrical instruments, 
such as one of the poles of batteries, the poles of arc 
lights and lanterns, in telephone and telegraph instru- 
ments, and the resistance elements in electric furnaces. 

INORGANIC COMPOUNDS OF CARBON 

Carbon unites readily with many other elements. In 
fact, there are many thousands of compounds of carbon. 
Therefore, in order to simplify the study of them, they 
are divided into two great groups, the inorganic and the 
organic. In general, the organic compounds are found 
in plants and animals, and the inorganic in the non-living 
world, although this distinction does not always hold. 

Carbon Dioxide. — We have already mentioned two dif- 
ferent combinations between carbon and oxygen. The 
ordinary one, carbon dioxide, is produced when carbon or 
a compound of carbon burns with plenty of oxygen pres- 
ent. Thus, it is formed during the burning of coal or 
charcoal in our stoves and furnaces, when wood is burned, 
when gasoline explodes, when coal gas, acetylene, alcohol 
and kerosene burn, and when food is burned in the animal 
body. As has been pointed out before, carbon dioxide is 
also formed when any acid acts on any carbonate. This 
is made use of in fire extinguishers (Fig. 20). The use 
of soda in cooking in connection with acids, as in sour 
milk and vinegar, is explained by the fact that the baking 
soda reacts with the acids to produce carbon dioxide, and 
this gas puffs up the dough and makes it light and porous. 
Baking powder is a mixture of an acid (tartaric or phos- 
phoric) and baking soda. As long as they are dry there 
5 



CARB N 



:- — -~ 

cylinder e©«- 



o reaction; on mixing with wet dough. 
however, carbon dioxide is generated as in the 
case of soda and sour milk above. When 
yeast raises bread dough, it generates carbon 
dioxide gas ; not by means of a carbonate, of 
course, but simply as a product of combustion, 
since yeast is a living organism and produces 
carbon dioxide when it consumes food, the 
same as any higher animal or plant. In the 
same way the effervescence or ** fizz " of beer 
and wine is due to the carbon dioxide pro- 
duced by the yeast during the fermentation. 
Large volumes of carbon dioxide can be 

?d in steel cylinders under pressure ; these 
cylinders are sold to soda fountains and to 
manufacturers of soft drinks to " charge " 
their drinks with "fizz Fig. 23). These 
cylinders are also used in fire extinguishers, 
as has been mentioned- 

The Carbon Cycle. — The story of carbon 
dioxide in nature is a rather remarkable one. 
an narrate here in a few lines what re- 
quired in nature millions of years. In the 
earlier history of this globe, there was a great 
deal more carbon dioxide in the air than there 
- : present. Also, a far greater proportion 
of the earth was covered by the seas. T: 

were alive with plant and animal life. 
The plants absorbed the carbon dioxide of the 
air. Minute sea-animals ate the plants and 
stored the carbon in their own bodies, put- 
g some of it into their skeletons as calcium 
carbonate. "When the animals died, the soft 
body parts decayed and the skeletons dropped 
to the bottom of the - a. A fter long series of 



THE CARBON CYCLE 



67 



years, the accumulations of these skeletons amounted to 
beds of calcium carbonate hundreds of feet thick in some 
places. These beds are our limestone, marble and chalk 
beds of to-day. Wherever calcium carbonate in one of 
these forms is found, it means that that region was once 
the bottom of a sea. Thus the carbon dioxide of the air 
passed through a plant life, then an animal life, then spent 



Higher 
animals 




Lime 
Kiln 



CaCO s 
of limestone 



Fig. 24. — Diagram showing the cycles of carbon. The carbon of the carbon dioxide in the 

air can be traced through the plant world, the animal world, the mineral world, to the 

industrial world, and thence to the air again. Shorter cycles can also be traced. 

ages and ages in the ground. Now it is mined as lime- 
stone; and when we "burn" limestone to make quicklime, 
the carbon dioxide is driven off again into the air, thus 
completing the ' ' cycle of carbon. ' ' There is an enormous 
amount of carbon dioxide stored up in the limestone of 
the earth, as this mineral constitutes whole mountains, 
and beds of it hundreds of square miles in extent are 
found in all parts of the world. Figure 24 shows this 
story of carbon in a diagrammatic way. 



68 CARBON 

The tact that when limestone is roasted to make quick- 
lime carbon dioxide is given off, provides us with a ready 
means of detecting carbon dioxide. When the quicklime 
is slaked in water, we gel the so-called limewater, which 
is a perfectly clear solution. When air, or any gas con- 
taining carbon dioxide, is passed into this solution it 
becomes cloudy because of the re-formation of cal- 
cium carbonate. 

The other oxide of carbon is called carbon monoxide. 
It is produced when carbon burns in an insufficient amount 
of oxygen; that is, only half as much oxygen combines 
with the carbon as when the dioxide is formed. The two 
equations involved bring this out: 

C + O = CO (carbon monoxide) 
C + 20 = CO,, (carbon dioxide) 

Since the carbon in the first instance is really only half 
burned, we might expect that carbon monoxide would 
undergo further oxidation; and indeed it does burn 
very readily : 

co + o = CO, 

On the other hand, when carbon dioxide is passed through 
red-hot carbon, the latter takes away a part of the oxygen 
from the dioxide, and carbon monoxide results : 

CO, + C = 2 CO 

carton dioxide red-hot coal carbon monoxide 

It is in this way that hard coal stoves are always produc- 
ing carbon monoxide, which burns wdth a pale-blue flame 
at the top of the pile of coal (Fig. 25). If the draft is 
too suddenly shut off from a very hot fire, the monoxide 
escapes into the room and often suffocates sleeping- 
people. For this oxide <>f carbon is extremely poisonous, 
acting on the red blood corpuscles in such a way that 
they can n<> Longer absorb oxygen from the lungs. It 



CARBORUNDUM 



69 



cannot be detected by its odor, for it has none ; but it is 
usually accompanied by sulphurous odors from the coal, 
which indicate when the stove is not working properly. 
Carbon monoxide is also emitted from volcanoes, and is 
one of the two gases in water gas (p. 54). 

Carborundum. — When sand, which is silicon dioxide, 



^^^= 




Fig. 25. — Diagrammatic section of a hard-coal stove. Fresh air enters at A ; the oxygen of 
the air combines with the carbon of the coal at B to form carbon dioxide; the carbon dioxide 
comes in contact with hot carbon at C, and is reduced to carbon monoxide. This, being an 
inflammable gas, burns with a pale-blue flame at the surface of the pile of coal by means 
of fresh oxygen entering at D. If no air is allowed to enter at D, the unburned gas passes 
out the chimney, or escapes into the room and poisons the occupants. 

Si0 2 , is fused in the electric furnace (Fig. 21), at a very 
high temperature with coke, part of the carbon combines 
with the silicon to form silicon carbide, or carborundum: 



Si0 2 +3C = 
sand coke 



SiC + 

silicon carbide 



2 CO 
carbon monoxide 



70 



CARBON 



This carborundum comes out as brilliant, beautiful, bluish- 
Mack crystals; they are extremely hard, and are used to 
make carborundum grinding stones and wheels. 

Carbide. — Another common carbide is one which is a 
compound of calcium and carbon. It is called calcium 
cq rbide, or, very commonly, simply carbide. It is produced 
by fusing quicklime and coke in the electric furnace. It 
is a very familiar substance, being used for generating 
acetylene, an inflammable gas. This has been mentioned 

before on page 56. The 
gas is used for illuminat- 
ing houses or other build- 
ings, and in bicycle and 
automobile lamps. In the 
latter cases it is dissolved 
in acetone and stored in 
steel cylinders. 

Carbon Bisulfide. — Car- 
bon combines with sulfur 
to form carbon bisulfide. 
This is a disagreeable 
smelling liquid, the vapors 
of which are highly inflam- 
mable and very poison- 
ous. The latter property enables it to be used as a 
poison for insects, gophers, prairie dogs, and vermin. 
Whon cotton soaked in the liquid is dropped into the bur- 
row, the heavy vapors flow down the hole and kill the 
occupants. Carbon bisulfide is used extensively in vulcan- 
izing rubber, making artificial silk, and dissolving sulfur. 

OBGAHIC COMPOUNDS or CABBON 

Iii taking up now some of the compounds of carbon 
with nitrogen, hydrogen and oxygen, we are confronted 
with an enormous task. Most of tie- substances in animal 




- 



-Apparatus used in the 
yea^t fermentation. 



ORGANIC COMPOUNDS OF CARBON 1\ 

and plant bodies are made np of these elements. The 
study of organic compounds alone forms such a huge 
branch of chemistry that it is almost a science in itself. 
It is called organic chemistry, because in the early history 
of these compounds it was thought that they were found 
only in plant and animal bodies and were thus the prod- 
ucts of organic life. Since then, however, thousands of 
such compounds have been made artificially that have 
never been found in plants or animals. Among these are 
many drugs, most of our dyes, explosives, some flavoring 
substances, disinfectants, artificial silk, and photographic 
chemicals. Then, too, many natural compounds have been 
made artificially by organic chemists ; rubber, indigo, and 
the flavoring substance of vanilla and of many fruits are 
among these. 

Then, too, organic chemistry is of vital assistance in 
many manufactures, where the raw materials of nature 
are prepared for human food, clothing, shelter, and amuse- 
ment. Thus organic chemists control the processes of 
making granulated sugar from cane and beets ; of curing 
tobacco and blending the varieties to make various prod- 
ucts ; of malting and brewing ; of making corn syrup out 
of cornstarch ; of making various stock feeds as by-prod- 
ucts from flour and cereal mills ; of making artificial silk ; 
of distilling turpentine, petroleum, and perfumes; of 
making medicines, stock dips, insect poisons, disinfect- 
ants ; of canning fruits and vegetables ; of manufacturing 
candy, dairy products, soap, candles ; of the packing house 
industries, of the paint, oil and varnish factories. 

To state it all very briefly, organic chemistry has to do 
with all substances and materials that contain carbon, 
and with all the processes through which man puts them 
to fit them for his needs. Hence, if we can but begin to 
realize the universal abundance of the compounds of 
carbon, we will appreciate the necessity of knowing at 



72 

the A B O'a of organic chemistry. Therefore. Let 
insider for a while a few I classes of the c 

pounds of carbon. 

Hydrocarbons. — Firsl all the 1 he compounds 

>rbon with hydrogen alone. I ailed 

the hgdrocor 5. Mi thane, CH 4 , is the simplest. It is the 
*'fire damp" met with by miners, causing explosions in 
mines. It is also called " marsh gas," as it is the gas that 
bubbles up from the bottom of stagnant pools in hot 
weather. It constitutes the bulk of natural gas. and a 
large portion of coal gas. 

All the petroleum products are hydrocarbons : thus 
- i.ene is mainly C..H-..: h> > :Ve. C.H :< . and /:■ 
C- H__. Aa tyl< . I _:!_. is another. There are two im- 
portant hydrocarbons obtain - by-pr dn icts in the mak- 
ing of coal gas: they are f : \ C H . . and tol \ C 7 H 8 . 
It will be noticed that all of these compounds are highly 
inflammable: th istitute our most important liquid 

and gaseous fuels. This \s I expected, as > are 

of the two great ; -bon and 

hydrogen. Theoretically, therefore, when gasolene or 
any other hydrocarbon is burned completely, carbon di 
ide and water should be the only products formed : thus : 

-f 130 = 6 CO, + H/) 

These should have no particular odor. The exhaust g - - 
from a gasolene engine do have an odor, however, for at 
si two reasons : In the first place, the o stion mix- 

ture of gasolene vapor and air is seldom p : that is, 

there are not exactly 13 atoms of oxygen for each m 
cole of gasolene, - \s demanded by the a 
and hen< ire formed which do ha v 

In th a ad place, - of the lubricating oil in the 

cylinders Is - charred by the heat, and 

D odorous compounds and the "cylinder carbon." 



ALDEHYDES 73 

Paraffine, a solid, non-volatile petroleum product, has a 
molecule represented mainly by the formula C24P50; it 
will be seen that if this molecule could be decomposed 
into three or four parts, some of these parts would have 
about the same number of carbon atoms as gasolene. This 
is actually done in the process called i i cracking. ' ' Within 
the last few years chemists have been able to obtain con- 
siderably more gasolene from the crude oil by cracking 
the heavier constituents. 

Aldehydes. — The next simplest carbon compounds are 
those where oxygen enters into the molecule along with the 
carbon and hydrogen. There are many different classes 
of such compounds, each of which has many individual 
members. The first class is the aldehydes, the simplest 
member of which is formaldehyde, HCHO. Formalde- 
hyde is an irritating poisonous gas. When it is dissolved 
in water to make a 40 per cent solution, it goes by the 
commercial name of i ' formalin. ' ' This finds very impor- 
tant use in treating potato seed for scab, in disinfecting 
and fumigating rooms, barns, chicken houses, etc., and 
in preserving animal specimens for classroom study. 
There is another very interesting fact concerning for- 
maldehyde : it probably is the first product formed when 
green leaves manufacture sugar in the sunlight from car- 
bon dioxide and water. The equation involved is : 

C0 2 + H,0 = HCHO + 20 

As fast as the formaldehyde is formed, six molecules of it 
combine together to form one molecule of glucose sugar : 

6 HCHO = C 6 H 12 O c 
formaldehyde sugar 

Since the plant then uses this glucose to make all the 
other substances in its body, we can consider that for- 



71 CARBON 

maldehyde is the basic material from which all other plant 
constituents arc made. Another common aldehyde is 
Udehyde, ('..II-CHO. This gives the characteristic 
odor and flavor to peach and cherry stones; artificial 
almond, peach, and cherry flavoring extracts consist essen- 
tially of benzaldehyde. 

Alcohols. — The alcohols form another very important 
class of organic compounds. Among the great many mem- 

- of this class we can mention but a few. Methyl alco- 
hol, or wood alcohol, or wood spirit, as it is variously 
called, is CH .OH. It is produced, as we have learned 
re, when wood is roasted or distilled. It finds very 
great use in the paint and varnish industries, also as a 
fuel in small burners and in making formaldehyde. It is 
a strong poison. Ethyl alcohol, or grain alcohol, is 
C _ 1 1 -Oil. It is produced almost exclusively by the fer- 
mentation of sugar by yeast, according to the follow- 
ing equation: 

C. H, A = 2 C 2 H,OH + 2 C0 2 

dextrose alcohol carbon dioxide 

And since yeast cells are constantly present in the air and 
on trait, whenever fruit juices or other sugary solutions 
are exposed to the air alcoholic fermentation sets in. 
Wine and hard cider are made by this natural means of 
infection. In making alcoholic beverages from grains, the 
starch of the grain must first be converted into sugar. 
This is don.- by sprouting the grains, then mashing up 
the sprouted grain with water. Yeast is then added, and 
the fermentation allowed to proceed at the proper tem- 
perature. About 5 per cent of alcohol is usually produced. 
[f a beverage containing a much higher content of 
alcohol is wanted, the fermented mash is distilled, as was 
described a few chapters back. The first distillate is from 



ACIDS 75 

35 per cent to 45 per cent alcohol. This constitutes 
whiskey, brandy, etc., after it has aged in oak barrels for 
the proper length of time. If pure alcohol is wanted, two 
or three redistillations are employed, or else a special 
kind of single distillation. This gives a 95 per cent alco- 
hol, which is the most concentrated that is ordinarily 
found on the market. It is used in medicine, as a solvent 
for certain paints and chemicals, and in many other arts 
and industries. Since it is subject to a heavy government 
tax, however, it is too costly for most purposes. When 
it is " denatured, ' ' that is, made unfit for drinking pur- 
poses by the addition of some poisonous or bad-smelling 
substance, the tax is removed, and this cheapens the cost 
to the consumer considerably. This denatured alcohol 
now finds very extensive use in the industries and as a 
fuel in small lamps. Alcohol has a pleasant, aromatic 
odor, and a burning taste; taken into the body in small 
quantities it is a stimulant, but in larger quantities is 
a poison. 

Glycerin. — Another substance which is an alcohol, but 
which has entirely different properties from the two 
above, is glycerin. This is a constituent of all fats and oils 
of animal or plant origin. It is a by-product in soap 
manufacture. It is a white, syrupy liquid, used consider- 
ably in skin ointments. Its greatest use, however, is in 
the manufacture of nitroglycerin, the explosive, which is 
used alone or is absorbed on fuller's earth and pressed 
into sticks as dynamite. 

Acids. — The organic acids form another common class 
of substances, found very extensively in plants and ani- 
mals of all kinds. Formic acid, HCOOH, is the irritating 
substance in ants and stinging nettles. Acetic acid, 
CH 3 COOH, is the acid in vinegar. It is produced by a 
bacterium which, in feeding on the alcohol of hard cider 



76 CARBON 

and other fermented fruit juices, converts it into acetic 
arid. The following equation shows this: 

t.ll.M - 2 = C',H,0, + hx> 
alcohol oxygen acetic acid water 

This is very evidently an oxidation process. Everyone 
who has made vinegar knows that the fermented cider 
must be kept in casks which are not over one-half or three- 
fourths full, and that the casks must be kept open. We 
can now understand that this is because plenty of oxygen 
must be available to the vinegar bacteria for them to 
carry on their work. Acetic acid is also formed in silage 
and sauerkraut, and gives them their acid odor and taste. 

Butyric acid is formed when butter becomes rancid, 
and gives the latter its rancid odor. Stearic, palmitic, 
and oleic acids are the main constituents in most fats and 
nils; they will be mentioned later under that heading. 
Lactic acid is the sour milk acid, produced when the lactic 
acid bacterium ferments the milk sugar. It is also present 
in silage. Malic arid is the principal acid in apples, citric 
acid in lemons and gooseberries, tartaric acid in grapes, 
tannic aria" or tannin in tea and in oak and hemlock bark, 
and oxalic acid in rhubarb. 

Mention might be made here of that series of very 
delightful compounds which give flowers their odors and 
fruit- their flavors, and from which we make our per- 
fumes and incense oils. They are iriven the general name 
of esters <n/rl volatile oils. That they serve a useful pur- 
pose in nature cannot be doubted; they attract insects to 
flowers and thus help pollinate them; they give flavor and 
palatability to fruits and vegetables; spices help preserve 
foods: oil of eucalyptus, oil of turpentine, oil of cedar, 
rosin, wintergreen, peppermint, vanilla, oil of lemon, of 
orange, of cloves, of roses, are all useful. The world is 
more Interesting and pleasant because of these. 



SUMMARY OF THE CHEMISTRY OF CARBON 77 

Among the more complex compounds of carbon, hydro- 
gen, and oxygen are the carbohydrates and the fats and 
oils. As these are of primary importance in human and 
animal foods and in many agricultural occupations, they 
will be accorded more space and detail in Chapter XV. 
The same will also be done with the compounds in which 
nitrogen also enters into the composition, with the excep- 
tion of the following two compounds : 

Hydrocyanic Acid. — When one atom each of carbon, 
nitrogen, and hydrogen unite, there is formed the very 
simple substance of the formula HCN. Its chemical name 
is hydrocyanic acid; its common name is prussic acid. 
From its name it will be recognized as the well-known 
deadly poison. In fact, it is one of the most deadly poisons 
known. In nature it occurs in the young plants of 
sorghum cane, and often kills cattle which eat it ; in bitter 
almond oil ; in small amounts in peach and cherry stones ; 
in flaxseed, where it is poisonous in the oilmeals of cattle 
feed unless they have been heated in the process of manu- 
facturing, which destroys the poison. Hydrocyanic acid is 
obtained from potassium cyanide, or prussiate of potash ; 
it is used in fumigating buildings, greenhouses, orchard 
trees, and flour mills to rid them of insects (Fig. 27). 

Cyanamide. — A compound of carbon with calcium and 
nitrogen is calcium cyanamide, CaCn 2 , a substance un- 
known a few years ago, but one that is rapidly coming into 
use as a nitrogenous fertilizer. 

Chloroform and iodoform are two other compounds 
which do not fit into any of the above classes of organic 
compounds. The element chlorine enters into the first, 
and iodine in the other substance. Thus chloroform is 
CHCI3, and iodoform is CHL. Chloroform is the familiar 
anaesthetic, and iodoform is a disinfectant commonly used 
in hospitals. 

Summary of the Chemistry of Carbon. — In glancing back 



7s 



CARBON 



through the contents of this chapter, the student may 
express surprise at the great variety of subject matter 
grouped together under the heading ' ' carbon "; there is 
diamond and charcoal; the poisonous gas, carbon monox- 
ide: fire extinguishers; the "fizz" of soft drinks; lime- 
stone beds; petroleum and natural gas; carborundum 
grindstones; gopher poisons; prussic acid; sugars; per- 




Fn;. 27. — Tent over orange trees for fumigating with hydrocyanic acid gas to kill scale 

insects. This method is more common in California than elsewhere. The gas is either 

generated by dropping sodium cyanide into sulfuric acid, or liquid hydrocyanic acid is 

purchased direct. (From Farmers' Bui. 923, U. S. Dept. Agric.) 

tin ixs; fats; alcohol; the acid of silage; anaesthetics. It 
is well if such an impression has been received by the 
student, since it will serve to emphasize that carbon has 
nunc or less rightly been termed the "universal element.' ? 
Carbon is very abundant in the earth in the form of 
many useful minerals, oils, and coals; it is even more 
abundant in all animal and plant bodies. Indeed, carbon 
Le the main connecting link between the living portion of 
the world and the non-living portion, for the great masses 
of non living forms of carbon in the earth no doubt had 



SUMMARY OF THE CHEMISTRY OF CARBON 79 

their origin, some time in the past, in the remains of dead 
animals and plants. Then, as we take coal from the 
ground, burn it, throw the carbon dioxide produced into 
the air, and grow plants which absorb this carbon dioxide 
again, are we not really bringing the dead carbon back 
to a living form again ? This is done in still another way. 
We saw that the minute sea animals eat plants, which 
get their carbon from the air; the animals store some of 
this carbon in their skeleton in the form of calcium car- 
bonate ; the animals die, the skeletons drop to the bottom 
of the ocean and form limestone ; when we burn quicklime 
we drive the carbon dioxide out of the limestone, and 
return it to the air from whence it came in the first place. 
This carbon, then, has in turn served the life of the sea, 
the rocks of the earth, and the industries of civilized man. 
It may next be absorbed by a potato plant, and then eaten 
by man, and thus actually form a part of man's body itself. 
If atoms of carbon could speak, there would be some mar- 
vellous tales to be told, covering untold millions of years 
in time, and involving existence in air, rocks, and water, 
the strange plants and the freak animals of pre-historic 
times, in peat bogs, in the white-hot furnaces of the earth, 
and finally, perhaps, in a diamond in the crown of a king. 

These more or less fanciful facts are mentioned in 
order to illustrate the multitude of important functions 
that carbon and its compounds serve in the world. It is 
not only of fundamental necessity in all living tissues, 
but it is also intimately concerned with the inorganic 
or mineral world. 

The table on page 80 constitutes a summary of the 
chemistry of carbon and its compounds as we have dis- 
cussed it. A thorough study of this table will not only 
help to fix some of the facts in the mind, but it will aid in 
establishing the relation between the compounds and in 
acquiring a mental picture of the whole carbon world. 



80 



CARBON 



Table IV 

Summary of tin Chemistry of Carbon 





:.ula 


Where found or how- 
obtained 


Usee 


As the el em- 








Charcoal, lampblack. 


C 


By roasting coal, wood. 


Deodorant: decolorizer; 






bones, etc. 


printers' ink; fuel. 


Graphite 


C 


In mines, and made arti- 


Lubricant; electrical im- 






ficially 


plements. 


Diamond 


C 


In mines, and made arti- 
cially 


Jewelry; cutting glass and 




stone. 


Combined with oxygen: 








Carbon monoxide. . . . 


CO 


In coal stoves: in coal gas 


Fuel. 


Carbon dioxide 


CO! 


In air; by burning of 


Fire extinguishers; soft 






carbon 


drinks; raising bread. 


Combined \riih hydrogen: 








Methane, or marsh gas 


cm 


In mine gas; in coal gas 


Fuel. 


Gasolene 


C«Hi4 


From petroleum 


Fuel. 


Benzine 


C-Hi ? 


From petroleum 


Fuel. 


Kerosene 


CioHa 


From petroleum 


Fuel. 


Acetylene 


C-H. 


Action of calcium carbide 
on water 


Illuminant and fuel. 






Benzol, or benzine . . . 


C«H« 


From coal tar 


Fuel; solvent: explosives. 


Toluol, or toluene. . 


OrHi 


From coal tar 


Fuel: solvent; explosives. 


Naphthalene 


QmHi 


From coal tar 


Moth balls. 


Combined with carbon 








and oxygen: 








Formaldehyde 


CHtO 


Oxidation of wood alcohol ; 
produced in plants to 
form sugar 


Disinfectant. 








Benzaldehyde. . 


C«H 5 CHO 


Peach and ehenr stones 


Artificial cherry flavor. 


Wood alcohol 


CH40 


By distilling wood 


Fuel; varnishes. 


Grain alcohol 


CiH 6 


By fermenting starch or 


Fuel: preservative: sol- 






sugar 


vent: stimulant. 


Glycerin 


C*H s Oj 


In manufacture of soap 


In making nitroglycerin; 






cosmetic. 


Acetic acid 


CiHiOi 


In vinegar and silage 
In butter 




Butyric acid 


C4H,0! 




Lactic acid 


C»H 6 Oj 


In sour milk and silage 




Tannin 




In oak and hemlock bark; 


In making ink. 






in tea 




Starch 


Os 


In most seeds and tubers 


Food; laundering. 


Dextrose sugar 


CeHiiOe 


In corn syrup; in many 

fruits 
In sugar cane; sugar beet; 


Food. 


Cane sugar 


CisHsOu 


Food. 






maple sap 




Miscellaneous compound* 








Carborundum 




Made in electric furnace 


Grindstones. 


Calcium carbide. . . 


CaC- 


Made in electric furnace 


For making acetylene gas. 


Carbon bisulfide. . 


OS 


Made artificially 


Poison: vulcanizing rubber 


Hydrocyanic acid. 




In flaxseed: from potas- 
sium cyanide 


Killing insects. 


Chloroform 


CHCU 


Made artificially 


Anaesthetic. 


Iodoform 


CHI, 


Made artificially 


Disinfectant. 



QUESTIONS 

Bow does carbon occur in the air? In the earth? 

_ - involved in the formation of pure carbon in nature. 
What usee ha\ <■ diamonds ? 

What i- formed when graphite hum-? Write an equation. 
re diamonds made artificially.' 



LABORATORY EXPERIMENTS 81 

6. What is the principal use of graphite? 

7. Where did petroleum and natural gas probably have their origin ? 

8. How is charcoal made ? What are some of the by-products obtained ? 

9. How is coke made ? What are some of the by-products obtained and for 

what are they used? 

10. Describe how each of the oxides of carbon is produced, state when and 

how each can be produced from the other, and state what the im- 
portance of each is. 

11. Give three important uses of carbon dioxide, and state how the gas is 

prepared or handled in each case. 

12. How can one prove that there is carbon dioxide in the breath? How did 

it get there? 

13. Beginning with coal, describe by what process we can get acetylene gas 

for our automobile lights. 

14. State at least one use for each of the following: Carbon bisulfide, car- 

borundum, calcium carbide, prussic acid, methane, wood alcohol, kero- 
sene, formaldehyde, iodoform, glycerin, and acetic acid. 

15. How is pure alcohol made, starting with barley grain? 

16. How is denatured alcohol made, and what are its uses? 

17. Give briefly the story of an atom of carbon, beginning with the carbon 

in limestone and ending up with diamond. 

18. What has the science of organic chemistry done for our civilization? 

LABORATORY EXPERIMENTS 

20. To Show the Absorptive Power of Charcoal. — Roast several small 
pieces of charcoal in a covered dish, to drive out all absorbed gases. Then 
perform the following tests. 

(a) Place several pieces of charcoal in a test tube containing hydrogen 
sulfide water, or if this is not available, dilute ammonia water, shake for a 
few minutes, then filter, and test for the odor of hydrogen sulfide. Com- 
pare the amount of the odor with that of the water before treatment. In 
what other way can the absorption of gases by charcoal be shown? (Fig. 22.) 

(b) Repeat the above experiment using a solution of brown sugar or of 
litmus, boiling for a moment before filtering. What uses for charcoal are 
suggested by the results of (a) and (b) ? 

2i. The Preparation and Study of Carbon Dioxide. — Set up the ap- 
paratus shown in figure 11. Place in the generating flask several pieces of 
marble or limestone the size of peas. Pour dilute hydrochloric acid down 
the funnel. After about a minute collect the gas as was done in experiment 
12 and perform all the tests on it that were performed on hydrogen and on 
oxygen and record the results. Write the equation. Describe carbon 
dioxide, as to its color, inflammability, and density compared to air. Pass 
some of the gas into limewater. Where was this experiment performed be- 
fore? Close up all but one of the air-holes of a lighted Bunsen burner, and 
pass the jet of carbon dioxide into this hole. Explain the results. Place 
some baking soda (NaHC0 3 ) in a test tube, and add vinegar to it; then 
hold a lighted match over the mouth of the tube. How do fire extin- 
guishers work? 

22. To Demonstrate the Presence of Carbon in Various Sub- 
stances. — Heat separately in porcelain crucibles small amounts of the fol- 
lowing substances: Sugar, cotton, wool, sand, salt, soap, powdered lime- 

6 



82 CARBON 

and meat. What does blackening indicate? What kinds of sub- 
- will not blacken on heating! 

23. The Fermentation of Dextrose by Yeast. — (To be done by instruc- 
tor. 1 Place L60 c.c. of glucose Byrup in a liter flask with 500 c.c. of water. 
Add the following -alt- to Bupply mineral nutrient for the yeast; 2.0 g. 
potassium phosphate, 0.025 <:. calcium chloride, 0.025 g. magnesium sulfate 
and 2.0 g. ammonium sulfate. Mix a half cake of compressed yeast with 
water to form a thin paste and add this to the fla-k. Fit the flask with a 
stopper and bent glass tube as shown in figure 26. Put clear limewater in 
the cylinder with a thin layer of kerosene on the surface. Stand the 
apparatus in a warm place for several days, noting the appearance of the 
limewater at frequent intervals. Explain the results. What is the purpose of 
the kerosene? After the fermentation has proceeded several days, decant the 
clear portion of the liquid in the flask into a distilling flask and distill off 
about 200 c.c. Redistill this 200 c.c. to 100 c.c. and this to 50 c.c. Xote the 
odor of this distillate. Test its inflammability in a warm, shallow dish. If 
it does not burn, distill again, and test the first 10 c.c. with a match. Per- 
form the iodoform test for alcohol as follows: Make a 1.0 per cent solu- 
tion of alcohol from the reagent bottle. Put 10 c.c. of this in a test tube, 
and 10 c.c. of the distillate obtained above in another test tube. Into 
each tube put 2 or 3 very -mall crystals of iodine, then 5 c.c. dilute sodium 
hydroxide. Warm gently. A yellow precipitate, or a yellow color, and a 
characterise iodoform odor, or "hospital smell," indicate the presence of 
alcohol in the original solution. Write the following equations: (1) The 
action of the carbon dioxide in the limewater. If the precipitate that first 
formed in the cylinder redissolved later, see page 102 for the reaction. (2) 
The fermentation of dextrose into alcohol and carbon dioxide. 

24. To Study Formaldehyde. — (a) Into some methyl (wood) alcohol 
in a test tube drop a red-hot coil of copper wire. After the flame has ceased 
note the odor of formaldehyde. The heating of the copper causes it to oxidize 
slightly, forming copper oxide; the oxygen of this oxide then combines with 
2 hydrogens of the alcohol. Note the brightness of the copper after the ex- 
periment. The equation is: 

CH 4 -f O = CILO + H,0 
methyl formaldehyde 

alcohol 

(b) Add about 5 g. of potassium permanganate to 10 c.c. of formalin 
in a beaker. Xote the evolution of formaldehyde gas. This is the common 
nray ol generating the gas for fumigation. What is formalin? 

25. To Prepare Some Esters.— (a ) Mix a few c.c. each of ethyl alcohol 
and of acetic acid in a test tube. Add -lowly I or 2 c.c. concentrated sulfuric 
acid, mix gently and warm, Xote the fruity odor of ethyl acetate. 

Repeat, using ethyl alcohol and butyric acid. What fruit does this 
ester suggest ! 

Repeat, using methyl alcohol and salicylic acid. What flavor is 



CHAPTER VII 

ACIDS, ALKALIES AND SALTS 

From time to time in the preceding chapters we have 
had occasion to mention several acids, such as sulfuric, 
nitric, hydrochloric, and various fruit acids. The term 
acid is familiar to most people ; ask people who have never 
studied chemistry what an acid is, and a great many will 
say that an acid is something which tastes sour. And that 
is a fairly correct answer. For we may have the taste of 
substances described as bitter, sweet, biting, astringent; 
but the word sour conveys immediately a suggestion of 
green apples or cherries, vinegar, or sauerkraut, and these 
things we know are all acid-containing substances. 

There are other properties of acids besides sourness, 
however; and as acids form a very important class of 
chemical substances, and as a study of the properties of 
acids leads us to a study of the other important com- 
pounds, we shall now consider acids in some detail. 

Preparation of Acids, — A simple method of preparing an 
acid for study is to repeat the experiment in Chapter III, 
where a piece of phosphorus is burned under a bell jar 
standing in water. In this case it is easier to proceed as 
follows : a half inch of water is put into a wide-mouthed 
bottle provided with a cork. (A glass one-pint fruit jar 
will do.) A flat cork is floated in the water and a piece 
of phosphorus the size of a pea placed on the cork. The 
phosphorus is lighted, and the bottle closed. When the 
phosphorus has ceased burning the bottle and contents are 

83 



M \( IDs. Al.K \I.Ii:> AND SALTS 

shaken until all the tunics of the burned phosphorus are 
dissolved in the water. The water is then poured into a 
beaker. This water now has a sour acid taste, suggesting 
that the burned phosphorus had dissolved in the water to 
form an acid. Although we have mentioned before the 
chemical equations involved in this experiment, we repeat 
them here : 

•2 p + .-) o = p,o 5 

phosphorus oxygen phosphorus pentoxide 

1\<> + 3HeO = 2H 3 P0 4 

phosplioru- pentoxide water phosphoric acid 

It is the phosphoric acid, H..P0 4 , that gives the water the 
Bour taste. 

If, now, we put a piece of blue litmus paper into the 
water, the paper will be turned pink. This is another test 
for acidity ; in fact, it is the commonest chemical test for 
acids which we have. Litmus is the colored juice of 
certain lichens ; when strips of filter paper are soaked in it 
and dried, we have our ordinary litmus test-paper. 

The above experiment may be repeated, using sulfur; 
an acid solution will again be obtained. It has already 
been explained how nitric acid is produced in thunder- 
storms (p. -0) by the oxidation of nitrogen and then 
the solution of the nitrogen oxide in water. The common 
name for carbon dioxide is carbonic acid or carbonic acid 

: this is because solutions of the gas in water taste 
Bomewhaf sour, as in all of our soft drinks. The carbon 
dioxide actually forms a compound with the water of 
the Formula I !,<<>. 

Examples of Acids.— We might name many other acids 
and their methods of Formation, but we have named 
enough of them t<> !><• able to point out certain other charac- 



PREPARATION OF ALKALIES 85 

teristics, especially if we assemble a number of common 
acids with their formulas in a list : 



Phosphoric acid 


H 3 P0 4 


Nitric acid 


HN0 3 


Sulfuric acid 


H 2 S0 4 


Carbonic acid 


H,C0 3 


Hydrochloric acid 


HC1 


Acetic acid 


HC 2 H 3 2 


Tartaric acid 


H,C 4 H 4 O f 



Properties of Acids. — If we look at the formulas of the 
above acids, we will see that they all contain hydrogen. 
Some have one atom, some two, some three. These hydro- 
gen atoms are called acid hydrogens. In the formulas of 
the last two acids the hydrogens are written in two 
groups ; only the first ones, however, are to be considered 
as acid hydrogens, for reasons which will soon appear. 

On looking again at the above formulas, we see that 
other elements making up the acid molecules are never 
metals, but are always non-metallic elements. Thus, in 
the above acids we see phosphorus, nitrogen, sulfur, car- 
bon, and chlorine. Oxygen is sometimes, but not always, 
present. We can make a general statement to the effect 
that every acid is a compound of a non-metallic element. 

Summary of Acids. — We have now mentioned several 
characteristics of acids, which serve to distinguish this 
group of compounds from all other chemical substances. 
A summary of these characteristics is as follows : 

1. Acids are sour to the taste. 

2. Acids turn blue litmus paper red. 

3. The molecule of every acid contains at least one 
hydrogen atom. 

4. Every acid is a compound of a non-metallic element. 
Preparation of Alkalies. — If we now consider some of 

the characteristic features of compounds of metals, we 
find something entirely different from the above. If we 
take a piece of sodium, which is a metal, although not 



86 ACIDS. ALKAIJKH .\ND SALTS 

b sadly like iron, and place it in a little water in a 

there will be a violent reaction, with the final 

- 'pearance of the sodium. If the pink litmus paper 

I in the acid experiment is put into the water, it 

will turn blue. If the water is sted it will be found 

. ve not a sour taste, but a brackish, caustic, puckering 

. The ><><lium has evidently combined with the water 

to form a compound entirely different from an acid. Th is 

5 pink litmus paper bl f ii died 
an a~ 

The reaction involved with the sodium is as follows : 

Xa - PLO = XaOH - H 

rim wal - Liumhydr - hydr _ 

The hydrogen ee pes - gas, and leaves the sodium 
bs olved in the water. This sodium hydroxide 
is the ordinary caustic alkali, or caustic soda. Another 
alkali can be made by dissolving a little quicklime 
in water: 

CaO - H/_> = 

l.-klime (calcium ox: water calcium hydrate 

ition or tdrate is a mild alkali; it is the 

common limewater often taken for stomach trouble. 

A list of some common alkalies and their for- 
mulas folio" 

ium hydrate XaOH 

hydrate K< »H 

►H), 

;.per hydr Cu(OH), 
Cal'ium hydrate 

Ammonium hvdrate XH/>H 

Lead hydrate" Phc 

Properties of Alkalies. — Let ofl examine this list aa we 
did the list Is. In the first plac - that the 

alkalies <!<» i tain a hydrogen alone, as did th 



FORMATION OF SALTS 87 

but they do contain a hydrogen and an oxygen together. 
This OH is the hydrate group. Thus every alkali is a 
hydrate. The term hydrate comes from the fact that such 
a compound is usually f ormecf from water, as in the case 
of the sodium and the calcium hydrates above. 

The next thing we notice is that each of the above 
alkalies is a compound of a metal and not a non-metal. 
There are, in the above list, sodium, potassium, iron, cop- 
per, calcium, and lead. The nitrogen of the ammonia is 
not a metal, to be sure; but ammonium hydrate turns 
litmus blue, and the NH 4 group acts like a metal chemi- 
cally in a great many ways. The above list might have 
been extended to include almost all of the metallic ele- 
ments. It must not be thought that all of them form 
hydrates that are soluble in water, like those of sodium 
and calcium. But the general statement can be made that 
the alkalies are compounds of the metals with the hy- 
drate group. 

Summary of Alkalies. — We can now summarize the char- 
acteristics of alkalies as we did those of acids : 

1. Alkalies do not taste sour, but cause a brackish, 
puckering sensation in the mouth. 

2. Alkalies turn litmus paper blue. 

3. The molecule of every alkali contains at least one 
hydroxyl, or OH, group. 

4. Every alkali is a compound of a metallic element. 
Formation of Salts. — If a piece of litmus paper is 

dropped into a little dilute acid in a beaker and some 
dilute alkali is added, a little at a time, with constant 
stirring, the litmus paper will remain red until a certain 
amount of alkali has been added, when it will turn blue. 
Evidently the acid has been destroyed, so that alkali now 
exists in the beaker and exerts its effect on the litmus 
instead of the acid. If the alkali is added very carefully, 
a point can be reached where the litmus is neither red nor 



88 ACIDS, ALKALIES AND SALTS 

blue, bul a tint intermediate between them. This point, 
where a solution is neither acid nor alkaline, is called the 
neutral point. That is, the alkali has neutralized the acid; 
or conversely, the acid has neutralized the alkali. 

Let us illustrate this by means of sodium hydrate and 
hydrochloric acid, and use a chemical equation: 

XaOll + HC1 = NaCl + II 

Bodium hydrate hydrogen chloride sodium chloride water 

The hydrogen of the acid combines with the hydrate group 
of the alkali to form water, which leaves the non-metallic 
clement, chlorine, of the acid, to react with the metallic 
element, sodium, of the alkali, to form the sodium chloride. 
This latter compound will be recognized as common salt. 
In fact, it is a salt; that is, it is one of a large class of 
substances called salts. All salts are combinations of a 
metal with a non-metal, hence a great many different salts 
arc possible. Epsom salt, saltpeter, Glauber's salt, are 
common examples of salts other than common table salt. 
Neutralization. — The above equation is typical of the 
chemical changes that always take place when an acid 
and an alkali act on each other. That is, when an acid 
and an alkali neutralize eaeli other, a salt and water are 
at tea ijs formed. A few other examples of neutralization 
will be given: 

NaOH -f UNO, = NaNO, + HX> 

sodium. hydrate nitric acid sodium nitrate (saltpeter) water 

2NaOB + H,S(), = Xa,so, +2H 2 

Bodium hydrate Bulf uric acid sodium sulfate (Glauber's salt) water 

Oa(OH), + M ( o = CaCO, + 2H 2 

calcium hydrate carbonic acid calcium carbonate water 

II will be noticed that one acid hydrogen always com- 
bines with one hydrate group to form one molecule of 
water, tf, as in the second equation, the acid happens 



RADICLES 89 

to have two hydrogens, and the alkali only one hydrate 
group, two molecules of the alkali have to be used to 
satisfy the acid. 

In looking at the formation of a salt carefully, it will 
be seen that it actually consists of a metal replacing the 
hydrogen of the acid. Thus, some of the salts of hydrogen 
nitrate (nitric acid) are sodium nitrate, copper nitrate, 
lead nitrate, silver nitrate. Hydrogen sulfate is sulfuric 
acid; some of its salts are tin sulfate, nickel sulfate, 
potassium sulfate. 

Neutralization is a very common and important chemi- 
cal reaction. When a soil becomes acid, it is neutralized 
with lime. When a fruit or food is too sour, it is neutral- 
ized by means of baking soda, a mild alkali. If our 
stomach becomes too acid, we take limewater to partially 
neutralize the acidity. If we spill acid on our clothes or 
body, we are always told to put soda or ammonia on it to 
neutralize it. The buttermaker can measure the amount 
of acid formed in sour cream by finding out how much 
alkali is required to neutralize it. 

Sugar is not an alkali. Therefore, when it is used to 
sweeten sour fruits, it does not neutralize their acidity; 
it simply masks their sourness, so that we taste the sugar 
instead of the acids. 

Radicles. — In discussing acids we found that an acid 
consists essentially of a non-metal combined with hydro- 
gen. The non-metal may exist alone with the hydrogen, 
as in HC1, where chlorine is the non-metal, or the non- 
metal may be linked with some oxygen atoms, as in HN0 3 ; 
or it may be linked with a still larger group, as in 
H 2 C 4 H 4 6 (tartaric acid), where the four carbon atoms 
are the non-metal and are a part of the whole group 
C 4 H 4 G , only the first two hydrogens being acid hydrogens 
and replaceable by a metal. Thus some of the salts of 
tartaric acid are CaC 4 H 4 O ri , K 2 C 4 H 1 6 , CuC 4 H 4 6 . These 



I N i ACIDS, ALKALIES AND SALTS 

groups are called the acid radicles. Thus the nitrate 
radicle is -N0 3J the phosphate radicle is -P0 4 , the acetate 
radicle is (\_ll ,()._., and the sulfate radicle is -S0 4 . 

Instead of defining a salt as the combination of a metal 
and a non-metal, we can now more accurately say that a 
salt is a compound consisting of a metal combined with an 
acid radicle. Another way of stating it is that a salt is an 
acid with the hydrogens replaced by a metal. We speak 
of the salts of sulfuric acid, meaning the compounds 
which are formed when various metals replace the hydro- 
gens of sulfuric acid. Or, we speak of the salts of copper, 
meaning the compounds which arise when copper replaces 
the hydrogen of various acids. 

Metals and Non-metals. — Up to now we have not 
attempted to distinguish between the chemical elements 
t hat are metals and those that are not metals. The chemi- 
cal elements can be roughly divided into these two classes. 
The metals are characterized in general by being solids, 
by having a metallic lustre, by conducting heat and elec- 
tricity readily, and by being capable of being drawn into 
wires. All the metals do not conform to all of these 
characteristics, to be sure, but in general these are true. 
Prom what we have just seen in connection with acids 
and alkalies, we can give a further chemical distinction 
between the metals and non-metals, and that is that non- 
metals form acid radicles, and the metals replace the 
hydrogen of acid. Thus, the chemical behavior decides 
whether an element is to be considered a metal or a non- 
metal. Sodium does not look any more like a metal than 
does phosphorus; but as it forms a strong alkali, and as 
phosphorus forms a strong acid, there is no mistaking 
the class to which each belongs. 

Valence. — The student by now may have noticed cer- 
tain irregularities in the proportions in which the various 



VALENCE 91 

elements and radicles are combined. We have NaOH, 
Ca(OH) 2 and Fe(OH) 3 ; we have HN0 3 , H 2 S0 4 , and 
H 3 P0 4 ; we have C0 2 , H 2 0, and S0 3 ; we have NaCl, CaCl 2 , 
FeCl 3 . That is, two hydroxyls or two chlorines combine 
with one calcium, whereas it requires three of them to 
combine with one iron, and only one for a sodium, and 
so on. < Different elements and radicles thus have different 
combining power. Suppose we represent each of these by 
a circle, with an arm on it for each combining power. We 
would have something like these: 



Hydroye/7 


& 


Oxyyen 


-<°> 


Hydrate 


(f) 


Ch/or/he 


@h 


Sodium 


©~ 


/ron 


Mr 


N/trate 


s>~ 


Sulfate 


-®y 




Phosphate 

When these atoms and radicles combine, let us imagine 
them joining hands. A hand of one never grasps more 



92 



ACIDS, ALKALIES AND SALTS 



than one hand of another, and all hands must be occupied 
when the compound is complete. Some of the above might 
combine as follows : 

(SK5X2) (5X2) (2XSX2) 

wafer hydroch/or/c oc/'d ca/c/u/7? cfi/or/tfe 

(OH) (Ofh (Fe 




su/furic oc/c/ 





iron /?/iosp/iafe 



iron hydra fe 



It must not be imagined that these atoms and radicles 
really have arms thrust out ready to unite with others; 
we have never yet been able to see an atom or a radicle, 
and do not know what the mechanism of chemical combina- 
tions is. But the above method illustrates the behavior 
of the elements, and it is useful for that reason. This 
combining power of elements and radicles has been given 
the name of valence. The hydrogen atom has a valence of 
one, the sulfate radicle two, and so on. 

Table V 

Valences of the Commoner Elements and Radicles 



Valence of I 


Valence of II 


Valence of III 


Valence of IV 


H 


Mg 


Al 




NH 4 


Ca 


Fe 




\;i 


Fe 






K 


Cu 






& 


Zn 






s 


P0 4 


Si 


I 


8( ), 






NOi 


( '< );; 






OH 





N 


c 



LABORATORY EXPERIMENTS 93 

If calcium has a valence of two, and chlorine of one, it 
will take two of the latter to satisfy one calcium. There- 
fore, the formula is CaCl 2 , and not CaCl or Ca 2 Cl. 

It is very important that the student memorize the 
valence of the more common elements and radicles. These 
are given in Table V. Only the simpler ones are given; 
some elements have two valences, and some have a valence 
as high as eight; but it would be useless to go into 
that here. 

The next table summarizes the characteristics of acids 
and alkalies. 

Table VI. 
Summary of Characteristics of Acids and Alkalies. 

Acids Alkalies 

1. Turn blue litmus paper red. 1. Turn red litmus paper blue. 

2. Taste sour. 2. Taste soapy and slippery. 

3. Contain H combined with a non- 3. Contain OH combined with a 

metallic element or radicle. metallic element or radicle. 

4. Combine with alkalies to form 4. Combined with acids to form 

water and salts. water and salts. 

QUESTIONS 

1. Write equations showing the reaction involved when each of the first five 

acids in the list on page 85 neutralizes each of the first five alkalies on 
page 86. Name the salt formed in each case. Pay close attention to 
the valence of each element and radicle. 

2. How could you neutralize- some vinegar in a beaker ? How would you 

know when it is neutral? 

3. How would you prepare calcium phosphate? 

4. What is the difference between a metallic and a non-metallic element? 

5. What is an acid hydrogen ? 

6. Explain why a fruit no longer tastes so sour after sugar is added to it. 

LABORATORY EXPERIMENTS 

26. To Study the Properties of Acids. — Prepare very dilute solutions 
of hydrochloric, nitric, acetic and tartaric acids. Test each one as to taste, 
effect on sodium bicarbonate, effect on litmus paper and on solutions of other 
indicators such as cochineal and phenolphthalein. To what element in the 
acids are these characteristics due? What other property of acids was shown, 
in experiment 12? 

27. To Study the Properties of Alkalies — "(a) Prepare very dilute solu- 
tions of sodium hvdroxide, calcium hvdroxide (limewater), and ammonium 



£4 ACIDS. ALKALIES AND - 

them a- roe performed on a 
experiment I hat are the characteristics due in this ea 

• apple, orange, or lemon, and divide H 
Carefully add -ome very dilute sodium hydroxide to one portion until 
it barely turns litmu- paper pink. Compare the taste of the two portions 
of ji: me of the acids in the treated portion? 

To Show the Colors of Indicators. — An indicator is a substance 

■which has a different color in acid from what it has in alkali. Record the 

f litmus. methyl orange, cochineal, phenolphthalein.and any other indi- 

- that are available, in acid and in alkaline solutions. Dip bruised 

irple cabbage in weak acid and in weak alkali and record the 

-. Hold various colored flowers over an open bottle of ammonia and 

an open bottle of hydrochloric acid. What would you say a* to the r*r 

(acid or alkalin- sap of these flowers? 

29. The Preparation of Common Salt. — Dilute 50 c.c. of concentrated 
hydrochloric acid with an equal volume of water. Then carefully add sodium 
tion 05 or 20 per cent) with constant stirring with a glass 
rod until tl - I u ju-t turns blue litmus paper pink. Evaporate this 
solution down : - in a porcelain evaporating dish. Taste tli- 

due. What is it? Write the equation showing its formation. What 

:e-troying an acid by an alkali called? What would have been 
formed in I f the following acids acting on each of the 

alkalies: HXO ; and H^S0 4 on XaOH, KOH. €a(OH .... XH 4 0H? 
Write equations. 



CHAPTER VIII 

THE LIGHT METALS 

Two Groups of Elements. — In the second chapter we 
learned that there are some eighty chemical elements 
known and that of these eighty only thirty are at all 
common. In this brief course, covering the chemistry of 
those elements which make up the substances in the little 
world in which we have our daily lives, we cannot study 
more than twenty of the elements. With these twenty, 
however, we ought to be very familiar. They make up the 
air we breathe, the water we drink, our food, clothing, 
building materials, the soil, the rocks, our drugs and 
medicines, our coins, paper, ink, toilet articles ; in short, 
everything that we ordinarily have to use. It is 
therefore important that we now take up a systematic 
study of these few chemical elements. About each one 
we want to know where and how it is found in nature, 
how we utilize it, and what its important compounds are. 
We naturally divide this group of elements into metals 
and non-metals, and shall consider each class separately. 

Simply for convenience, we shall divide the metals into 
groups, as follows : 

I. Light metals. 

1. Alkali metals. These include sodium and potassium 
and several rare elements. They are called alkali metals 
because their hydrates are our most powerful alkalies. 
We mentioned NaOH and KOH in the last chapter. 

2. Alkaline earth metals. This group includes calcium 
and magnesium, and the less important metals strontium 
and barium. They receive the name of alkaline earths 

95 



96 THE LIGHT METALS 

Prom the facts that they form fairly strong alkalies, and 
that they are very abundant in the earth. 

3. Aluminum. 

II. Heavy metals. 

4. Iron and others. This is not a definite chemical 
group ; under this heading we will discuss iron, lead, cop- 
per, tin, zinc, and mercury. 

5. The precious metals, silver, gold, and platinum. 
These metals are not only in limited amounts in the earth, 
but they are also very useful; hence they are called the 
precious metals. 

1. Alkali Metals. — Sodium. — Sodium is a very abundant 
metal, constituting over two per cent of the earth's crust. 
It never occurs as the free element, for it has a powerful 
chemical attraction for many other elements. We saw in 
the last chapter that it combines violently with water. 
Common salt, XaCl, is its most abundant compound; sea- 
water is over three per cent sodium chloride, Great Salt 
Lake water contains from fifteen to twenty per cent of it; 
there are many other large salt lakes and marshes in the 
world, and there are enormous beds of the dry salt in many 
parts of the world, particularly in Michigan and Xew 
York in this country. This salt is used as the source of 
most of the other compounds of sodium. 

Sodium Hydrate. — Although chemically sodium is a 
metal, the element itself cannot be used like other metals. 
It is soft, like putty, oxidizes to a powder readily in the 
air, and combines with water to form sodium hydrate. 
This sodium hydrate or caustic soda is used in very large 
quantities for making soap, and is used in small amounts 
in liquid soaps, which gives the latter their roughening 
< i'l'iTt on the skin. 

Salts of Sodium. — As we said in the last chapter, the 
characteristic of all metals is that they form salts by com- 



POTASSIUM 97 

bining with acids. The salts of sodium are many and 
useful. With hydrochloric acid it forms the sodium chlo- 
ride mentioned above. This is used for flavoring foods, 
for preserving meats and fish, for making a freezing 
mixture with ice, for glazing pottery. With nitric acid 
sodium forms sodium nitrate, N"aN0 3 , or Chile saltpeter. 
This is found in large beds in Chile ; it is used mostly as 
a fertilizer because of its nitrogen content, although a 
great deal is mined for use in making nitric acid. Sodium 
sulfate, Na 2 S0 4 , is called Glauber's salt; it is commonly 
used as a veterinary laxative, in making glass, and in 
making sodium carbonate. Sodium carbonate, Na 2 C0 3 , 
commonly called washing soda or sal-soda, is the main con- 
stituent in washing powders and in water softeners. It 
is also used in large amounts in making glass and soap. 
The "black alkali" of some soils is due to sodium car- 
bonate. Sodium bi-carbonate, XaHC0 3 , is baking soda. 
It is much used in cooking, and is always one of the con- 
stituents of baking-powders. Sodium hyposulfite, Na 2 S 2 3 , 
is the ordinary "hypo" fixative of photography. Borax 
is sodium borate, used in softening water and for other 
laundry purposes. Sodium silicate is the "water-glass" 
with which we preserve eggs. All ordinary hard soaps 
are salts of sodium with certain acids obtained from fats. 
Sodium compounds are found in the bodies of all plants 
and animals; they are not essential to the plants, however. 
Potassium. — The compounds of potassium are mostly 
duplicates of those of sodium, since the two metals are 
very similar in their chemical properties. Potassium 
compounds, however, are not nearly so easily obtained as 
those of sodium, as most of the potassium in the earth is 
combined in the granite and feldspar rocks. All soils 
contain small amounts of potassium. The one great 
source of potassium salts is the Stassfurt mines in Ger- 
many; and since the whole world was dependent on these 

7 



96 THE LIGHT METALS 

mines for its potash, the World War created potash star- 
vation in many countries. The United States had to dis- 
eover some other sources of supply, and succeeded in 
obtaining fairly large amounts from sea-weeds, from blast- 
furnace residues, and from certain saline lakes in Califor- 
nia. Sea-weeds are high in both potassium and iodine, 
a substance much used in disinfecting wounds. The weeds 
are gathered, dried, and burned, and the potassium and 
iodine compounds extracted from the ash with water. 

Potassium Hydrate. — Metallic potassium is very similar 
in its properties to sodium. "With water it forms potas- 
sium hydrate, KOH, the powerful caustic alkali mentioned 
in the last chapter. It is used in dehorning cattle to some 
extent, also in making soft soap. 

Salts of Potassium. — Potassium chloride is found in 
small amounts in sea-water, and in larger amounts in the 
Stassfurt beds. Its commercial name is- muriate of 
potash, and is largely used as a fertilizer. Potassium 
nitrate, KN0 3 , is ordinary saltpeter, used in corning beef, 
as a fertilizer, and in making black gunpowder. In the 
latter case it serves as an oxidizing agent to oxidize the 
other two constituents of the powder, charcoal and sulfur. 
Potassium sulfate, K->S0 4 , is a more common fertilizing 
material than the chloride; it is also used in making hard 
glass. Potassium carbonate, KoCO :; , is the lye from wood 
;i>hrs, used in making soft soap. The latter is the potas- 
>ium salt of the acids found in fats. Fresh hard wood 
ashes contain from six to eight per cent of K 2 C0 3 , and 
hence arc valuable fertilizing material. Potassium cya- 
nide, KCN, as well as sodium cyanide, NaCN, are used 
in generating hydrocyanic acid gas for fumigation (Fig. 
27 . Thus: 

_'K< \ + II so, = 2HCN + K so, 

iimi cyanide sulfuric acid hydrocyanic acid potassium Bulfaie 



QUICKLIME 99 

Potassium compounds are found in all plant and animal 
bodies, and are essential to the life of all organisms. 

2. The Alkaline Earth Metals.— Calcium. — Calcium and 
magnesium occur mostly as their carbonates in nature. 
Calcium carbonate, CaC0 3 , is limestone. We have dis- 
cussed in a previous chapter the origin of the immense 




Fig. 28. — A limestone quarry. Such beds of calcium carbonate are the result of accumula- 
tion of the skeletons of minute sea-animals for thousands of years. That these land areas 
were once the bottom of the ocean is proved by the fact that fossils of sea-animals are 
frequently found in them. (From Bui. 230, Wis. Agri. Esp. Station.) 



limestone, chalk, and marble beds (Fig. 28). Marble is 
crystallized limestone ; the change was brought about by 
great heat and pressure in the earth. Chalk is another 
form of calcium carbonate found in nature. Bo.th marble 
and limestone are valuable building materials. 

Quicklime.— -Limestone finds its greatest use, how- 



100 THE LIGHT METALS 

ever, as the source of quicklime, and thus of our building 
mortar and our whitewash. Lime plaster is such a famil- 
iar substance that its chemistry should be understood 
from beginning to end. When the limestone is "burned" 
or roasted, in kilns or piles, as in figure 29, to about 




Iii. 29. — A home-made kiln for burning oyster shells to quicklime. Similar improvised 
outfits "an be used for burning other forms of calcium carbonate, such as clam shells 
from button factories, limestone, marl and marble. (From U. S. Dept. of Agriculture, 

Farmers' Bui. 921.) 

1 lot) F., carbon dioxide is driven off and calcium oxide 

is left behind : 

CaCO = CaO + CO. 

calcium carbonate calcium oxide carbon dioxide 

The carbon dioxide escapes from the vent at the top. 
The calcium oxide is ({uicklime. One hundred pounds of 



LIME PLASTER 101 

good limestone make about fifty pounds of quicklime. The 
latter is in hard, porous lumps. It can be air-slaked or 
water-slaked. In the former it re-absorbs from the air 
the carbon dioxide it lost : 

CaO + C0 2 = CaC0 3 

Hence air-slaked lime is calcium carbonate, or the same 
chemically as limestone itself. When quicklime is slaked 
in water it unites with it as follows : 

CaO + H 2 = Ca(OH), 

calcium oxide water calcium hydrate 

If the proper amount of water has been added (100 pounds 
of lime to 30 pounds of water) the lime will crumble into 
a dry powder. This is the hydrated lime of commerce. 
This will dissolve to a slight extent in water to form a 
clear solution called limewater. This is a mild alkali 
used medicinally. If larger amounts of the hydrated lime 
are made into a thin paste with water it is called milk 
of lime. 

Lime Plaster. — It is this milk of lime which is mixed 
with sand and other materials for mortar. The wet mor- 
tar is spread on walls or between stones or bricks and 
allowed to ' ' set, ' ' This wet mortar chemically is a mix- 
ture of sand, water and Ca(OH) 2 . As the water evapo- 
rates it leaves the mortar porous ; carbon dioxide from the 
air can then seep in and react with the calcium hydrate 
as follows : 

Ca(OH) 2 + C0 2 =CaC0 3 + H c O 

Thus more water is produced; and at the same time cal- 
cium carbonate, the same substance as the original lime- 
stone, is gradually formed around the particles of sand. 
By the time the water has all evaporated and all the 
calcium hydrate has become carbonate, the mortar is 



102 THE LIGHT METALS 

"set." It consists now of a mixture of calcium carbonate 
-and, together with any coloring matter, hair, or other 
substance that was added to it. We now see that the cal- 
cium has "-one around in a circle," for it started out as 
the carbonate in the original limestone, then went to the 
oxide, then to the hydrate, and ended up as the carbonate 
again. Looking back at the source of the limestone beds, 
we can consider that the calcium carbonate that once 
formed the skeleton framework of sea animals now forms 
part of the framework of our dwellings. 

Origin of Hard Water. — There is another very important 
relation between calcium carbonate and carbon dioxide. 
The carbonate is practically insoluble in water; therefore 
water alone in seeping through limestone beds w T ould not 
dissolve much of it. But as water passes through the soil, 
it absorbs considerable carbon dioxide which is formed 
in the soil by the decay of organic matter. This water 
charged with carbon dioxide attacks the limestone in the 
following way : 

CaCO, + C0 2 +H 2 0= Ca(HCO,) 2 

calcium carbonate carbon dioxide water calcium bicarbonate 

This calcium bicarbonate dissolves readily in the water. 
The latter is now a "hard water." It forms a curd with 
soap, and leaves a residue in the bottom of tea-kettles and 
boilers I Pig. 30). When water containing calcium bicar- 
bonate is boiled, the reverse of the above equation 
takes place ; 

Ca(HCOa), — CaCO, + CO, + H 2 

The carbon dioxide is expelled, leaving the original cal- 
cium carbonate in the water. As it is insoluble, it settles 
out as a sediment ; and as the water no longer contains 
any calcium salt in solution it is now a "soft water." 
Such hardness of water, which can !><■ removed In/ boiling, 



PORTLAND CEMENT 103 

is called "temporary hardness." If the calcium salt in 
the water is calcium sulfate or chloride, it cannot be 
removed by boiling, and hence is "permanently hard." 

Formation of Caves. — The Mammoth Cave in Kentucky, 
as well as other caves in limestone regions, was made by 
carbonated water dissolving out big pockets in the lime- 
stone, according to the equation given. 

Plaster of Paris. — Besides the plaster involving calcium 
carbonate, described above, there is another plaster mate- 





Fig. 30. — Sections of steam or hot water pipes with deposit of lime from the use of hard water. 

rial which is a calcium compound. Plaster of Paris has 
the formula CaS0 4 %H 2 ; that is, the molecule of calcium 
sulfate has some water combined with it. When it is 
mixed with water to form a paste, it gradually combines 
with this water chemically to form a different combination 
of calcium sulfate and water. Thus : 

CaS0 4 %H,,0 + iy 2 H 2 = CaS0 4 2H 2 

The latter compound is the set plaster. It is the same as 
our gypsum, or land plaster, and it is also the same as the 
alabaster of Biblical mention. 

Portland cement is another calcium containing sub- 
stance which sets on treating with water. In this case com- 



104 THE LIGHT METALS 

plex silicates and aluminates are involved, into the cheniis- 
try of which we cannot go. 

Calcium silicate, together with sodium silicate, are the 
main constituents of our ordinary window and bottle glass. 
In making it, finely ground sand, calcium carbonate and 
sodium carbonate are mixed together and fused in fire- 
clay pots. The melted mass can then be poured into 
moulds or blown into any desired shape. Special kinds 
of glass contain potassium, borax, lead, cobalt, or 
other substances. 

Calcium Phosphate. — The bones of animals consist 
almost entirely of calcium phosphate. Ca 3 (P0 4 ) 2 . This is 
also found in great beds in the Southern States, and is 
there called rock phosphate. It is much used as a phos- 
phate fertilizer. Calcium is also found in all plants and 
is a necessary element in their growth. 

Bleaching Powder. — We mentioned under the subject 
of purification of water another important compound of 
calcium, the hypochlorite, CaOGL; great quantities of it 
are used as a bleaching agent in paper-making, cotton and 
linen mills, and straw-hat factories. 

Calcium Carbide and Sulfide. — In the chapter on carbon 
we discussed the manufacture and use of calcium carbide, 
I <i< \. and its reaction with water to form acetylene. An- 
other interesting compound of calcium is the sulfide, 
( !aS. After exposure to sunlight it will glow in the dark, 
and is therefore used in luminous paint on watch and 
compass faces and on the plates around keyholes. 

Magnesium. — The next metal of the alkaline earth 
group, magnesium, has great interest to us as the ele- 
ment as well as in compounds. Metallic magnesium burns 
readily in the air with a brilliant white light. When it is 
finely powdered and mixed with potassium chlorate, a 
powerful oxidizing chemical it burns in a fraction of a 



ALUMINUM 105 

second with a blinding flash of light. This mixture is the 
flashlight powder used in photography. Magnesium is 
also used in fireworks. 

Occurrence of Magnesium. — In nature the carbonate of 
magnesium is called magnesite. A very common way in 
which magnesium carbonate occurs is in dolomite, which is 
a mineral composed half and half of calcium carbonate 
and magnesium carbonate, CaC0 3 .MgC0 3 . Other well- 
known minerals are magnesium silicates, as talc, soap- 
stone, meerschaum, and asbestos. Some magnesium 
salts are found in sea-water, having been dissolved from 
the soil. It is a necessary element in both plant and ani- 
mal life; in fact, in plants it is a part of the chlorophyll, 
the green coloring matter, which is the substance that 
causes the union of carbon dioxide and water to 
form sugar. 

Magnesium oxide, MgO, is used as a mild alkali in 
medicine under the names "magnesia" and "cal- 
cined magnesia. " 

Magnesium sulfate, MgS0 4 , is commonly called Epsom 
salt, from the fact that it was first isolated from a spring 
at Epsom, England. It is used as a purgative. It occurs, 
very commonly in water, causing permanent hardness. 
Often it occurs to such an extent in waters that they are 
used directly as laxatives. Many waters in the Western 
States prove to be so strong with magnesium sulfate 
that they cannot be used for drinking purposes. They 
are often called "alkali" waters, although chemically 
there is nothing alkaline about magnesium sulfate. 

3. Aluminum. — Although aluminum minerals are ex- 
ceedingly abundant in the earth, more abundant, in fact, 
than those of any other metal, the metal itself has come into 
daily use only during the last fifteen years, since an elec- 
trical process of manufacture has greatly reduced its cost. 



106 



THE LIGHT METALS 



Aluminum ifi nstituent of all clays, granites, micas, 

feldspars, and slates. The metal cannot be prepared : 

them, however; only two minerals, of less abundant occur- 

• than the above, can be used in its manufacture. The 

metal is silvery white, rather soft, very malleable and due- 




Fig. 31 9 ■ a clay mine. The flay it removed in a way similar to coal — by drilling, 

blasting, picking, and carrying "lit of the mine on cars. The above cut is from a Pennsylvania 

firebrick clay mine. 



tile; it takes a fairly good polish, but the polish does not 
remain, as aluminum is slowly oxidized in the air with 
th<- formation of a grayish coating. When heated, alumi- 
num unites very readily with oxygen; in fact, it will take 
gen away from iron oxide, with the liberation of 
a great amount of heat. This property is utilized in 



CLAY 107 

thermite welding. Thermite, which is a mixture of pow- 
dered iron oxide and aluminum, is placed around the two 
iron parts to be welded, such as the ends of rails, and the 
thermite ignited. The reaction proceeds with such vio- 
lence that the ends of the rails are melted and fuse to- 
gether. The reaction is as follows : 



Fe 2 3 + 2A1 = A1 2 3 + 2 Fe 

iron oxide aluminum aluminum oxide iron 



Aluminum is used in enormous quantities in making 
cooking utensils, cables for electric wires, and the frames 
of cameras. 

Alum. — The alums are the most important salts of 
aluminum. There are many different alums, and they 
serve varied purposes, among which we might mention 
the dye industries, where alum helps to fix the dye in the 
cloth; water purification, where alum unites with the 
coloring matter and organic impurities and carries them 
down in a sludge; and in medicine as an astringent to 
check the flow of blood from wounds. 

Clay. — The pottery and brick industries use compounds 
of aluminum found in all parts of the world, which go by 
the general name of clays (Figs. 31, 32 and 33). They 
are essentially aluminum silicates with some water com- 
bined with them to form part of their molecules. When 
wet, clays can be moulded into any desired shape; and 
when baked in ovens, they become hard and strong, and 
will not again soften with water. What the exact chemical 
change is that takes place during the baking is not known. 
The glaze on pottery has a composition similar to that of 
glass ; it is formed by soda, lime, salt, and other substances 
reacting with the silica of the pottery during a sec- 
ond baking. 



108 



THE LIGHT METALS 




FlG. .'^2. — Moulding bricks preparatory to drying and baking. The raw clay is ground with 

uatcr by machinery. It is then moulded by hand into the crude bricks at the left of the 

picture. The machine moulds the finished bricks and stamps on them the manufacturer's 

mark. They are then stacked on the floor to dry, and later are baked. 




Kill ised for firing brick. They are brought to the kilns after drying for several 

well-ventilated sheds. The raw day is essentially an aluminum ailicate chemically 

combined with water. During the baking the water is lost and the clay is left in a condition 

is which it will not again take up the water. The fuel piped to these ovens ie natural gas. 



PROPERTIES OF THE LIGHT METALS 



109 



Table VII 

Summary of the Properties of the Light Metals 



Metal 



Where found and in what prin- 
cipal form 



Uses of the metal and its compounds 



Sodium . . . 



Potassium. 



Calcium. . 



Magnesium 



As NaCl in sea-water and 

in mines 
As Na 2 S0 4 in alkali soils 



As KC1 in sea-water and 
in Stassfurt mines in 
Germany 

In all granite rocks 



As CaC0 3 in limestone 

and marble 
As CaS0 4 .2H 2 in gypsum 
As Ca 3 (P0 4 ) 2 in rock 

phosphate and apatite 



As MgCOs in some lime- 
stones 

As MgClo in the Stassfurt 
mines in Germany 



Aluminum As silicate in all clays 



The metal has no important industrial 
uses. 

NaCl — to flavor food; preservative; 
glazing pottery. 

Na 2 S0 4 — veterinary purgative. 

Na 2 C0 3 — washing soda; glass-making. 

NaHC0 3 — baking soda. 

NaOH — soap-making. 

NaN0 3 — Chile saltpeter; fertilizer; 
gunpowder. 

Na 2 S 2 3 — hyposulfite in photography. 

Compounds of Na are essential to 
animal life but not to plant. ' 

The metal has no important industrial 
uses. 

KC1— fertilizer. 

K 2 S0 4 — fertilizer. 

K 2 C0 3 — in wood ashes; making soft 
soap. 

KOH — chemical industries. 

KN0 3 — saltpeter; corning beef; ex- 
plosives. 

KCN — fumigation for insects. 

Compounds of K are essential to both 
plant and animal life. 

The metal has no important industrial 
uses. 

CaO — quicklime, for lime mortar. 

Ca(OH) 2 — limewater as medicine. 

CaC0 3 — making quicklime; building 
stone; fertilizer. 

CaS0 4 . 1 ^H 2 0— plaster of Paris. 

CaS0 4 .2H 2 0— fertilizer. 

Ca 3 (P0 4 ) 2 — in bones and rock phos- 
phate. 

CaC 2 — carbide for making acetylene. 

Calcium compounds are essential to 
both plant and animal life. 

Mg — used in flashlight powder. 

Mg (OH ) 2 — milk of magnesia ; medicine . 

MgC0 3 .CaC0 3 -limestone for building. 

MgS0 4 — Epsom salt; medicine. 

Magnesium compounds are essential 
to both plant and animal life. 

Al — used for cooking utensils. 

Alums — medicine; dyeing; water puri- 
fication. 



110 THE LIGHT METALS 

QUESTIONS 

1. What are the differences between the metals and the non-metals? 

2. What do von think are the three most important compounds of sodium? 

Wl.\ 

3. Why are potassium compounds more important than sodium compounds 

in the life of the world ? 
I. Why is KNO, a more valuable fertilizer than NaNO,? 
~> What i- the most important use of CaCO.t? 
»;. Describe the chemistry of lime mortar from the limestone to the dry 

plaster. 
7 What i> the chemistry involved in the formation of a limestone cave? 
s. What is marble? Chalk? Dolomite? 
9. Now can temporary hardness he removed from water? Use a chemical 

equation to show the reaction. 
1(>. How is <;lass made? 

11. Which is the most useful as the free element, Na, K, Ca, or Mg? 

12. What do you think are the four most important compounds of calcium? 

Why? 

13. What do you think are the three most important compounds of mag- 

nesium? Why? 
1 \. Describe aluminum. 
1."). What are the most important uses of aluminum compounds? 

LABORATORY EXPERIMENTS 

30. To Study the Properties of Aluminum. — (a) Examine an alum- 
inum utensil. Is aluminum lighter or heavier than iron, copper, or silver? 
For what is aluminum used besides cooking utensils? 

(h) Obtain a piece of iron wire and one of aluminum, both of the 
Bame size and about j6 inches long. Holding one in each hand, insert the 
ends into a gas (lame and note which conducts heat the faster. How is this 
property of advantage in cooking utensils? 

(c) Heat some pieces of aluminum wire in 10 per cent sodium 
hydroxide solution in a test tube. Test the escaping gas with a match. 

Al + NaOH -f H 2 = Na Al 2 + 3 H 
sodium sodium 

hydroxide aluminate 

(di Repeat (c), using 20 per cent hydrochloric acid. 

Al + 3HC1 = A1C1, + 3H 

\\ bal are the two products formed? 

31. The Effect of Some Salts on Protein. — For a protein solution, 
make ;i solution of 1 pari egg white in 3 [tarts water. Pour about 5 c.c. 
of tin- solution into each of 7 test tubes. Test the solution with a few drops of 
the following -alt-: 1 I 1 Bodium chloride, (2) potassium chloride, (3) calcium 
chloride, (ti aluminum sulfate (alum will do), (5) silver nitrate, (6) 
mercuric chloride (llgCl,), (7) lead acetate. Record which jnetals form 
a precipitate with the egg white. Why is raw and not cooked egg white a. 



LABORATORY EXPERIMENTS 111 

good antidote for mercury, lead, and silver poisoning? Explain the action, 
of alum in stopping the bleeding of a cut. 

32. To Prepare Plaster of Paris. — Heat some gypsum, CaS0 4 .2H.O, in 
a porcelain or iron dish in an oven at 110° to 115° C. for 15 minutes. Do 
not let the temperature go over 115°. Cool, mix with a small amount of 
water and let stand until it sets. Write equations showing the formation 
of the plaster and the setting of the plaster. What uses has plaster 
of Paris? 

33. To Make Quicklime. — Heat some powdered limestone or marble 
in a porcelain crucible as hot as possible in the Bun sen flame for half an 
hour. Cool, then cover with water and note whether it slakes. If the slak- 
ing is not vigorous, it is because a sufficiently high temperature was not 
obtained for making quicklime. Test with litmus paper. An alkaline re- 
action shows the presence of some quicklime. Why? Wiite equations for 
the " burning " of the limestone and for the slaking in water. 

34. To Study the Slaking of Lime. — Grind up about 50 g. of fresh 
quicklime into small pieces. Divide into two portions. Place one portion 
in a well-stoppered bottle and expose the other portion to the air in a shallow 
layer in an open dish. Two days later cover each portion with water in 
test tubes, warm slightly, and note which slakes the more readily. Explain 
the chemistry of air slaking and of water slaking, giving equations. 

35. The Burning of Magnesium. — Hold a small piece of magnesium 
ribbon in the tongs and ignite in the flame. Write equation. For what 
is powdered magnesium used? 

36. The Preparation of Iron Sulfate. — Place 25 g. of iron nails in a 
flask, add about 35 c.c. of dilute sulfuric acid ( 1 part acid to 5 parts water ) . 
Warm until no more gas is evolved. There should be some undissolved iron 
left. Filter the solution, and then evaporate to one-half its volume. Cool, 
and allow the iron sulfate to crystallize out. Remove and dry the crystals. 
Describe them. Write the equation. What are the uses of this compound? 
To what class of chemical compounds does it belong? 

37. The Formation of Ink. — (a) Dissolve about 2 g. of the iron sulfate 
prepared in experiment 36 in 25 c.c. of water. Add a few c.c. of this solu- 
tion to a weak solution of tannin. The colored compound is iron tannate, 
the basis of most fountain-pen inks. 

(b) Make a strong extract of green tea by boiling a half teaspoonful of 
t~ie leaves in a test tube of water. Test this extract with the solution of 
iron sulfate. Taste the solution of tannic acid prepared in (a), then explain 
the puckering effect of strong tea in the mouth. 

38. The Effect of Carbon Dioxide on Calcium Carbonate. — Put a 
gram of powdered limestone into each of two test tubes, and add 10 c.c. of 
distilled water. Into one tube blow the breath through a piece of glass 
tubing for 5 minutes. Shake the other tube frequently. Filter each, and 
when the filtrates are clear, evaporate a 2 c.c. portion of each to dryness on 
watch crystals. Did the blowing of the breath increase ihe solubility of the 
calcium carbonate? How? Equation. How does this experiment illustrate 
conditions in the soil? How are caves formed? Boil the remainder of the 
filtrate containing the calcium bicarbonate in a test tube. Explain the 
origin of the precipitate. What has this experiment to do with hard 
water ? Boil some hard water in a test tube and compare with the above. 



CHAPTER IX 

THE HEAVY METALS 

The Iron Age.— Of all the dozens of metals that could 
be grouped under this heading, iron is preeminently the 
mosl useful and the most abundant. It occupies such a 
large place in our civilization that our age is called the 
"Iron Age," in contrast to those of the earlier races of 
man, who lived in the Stone Age and the Bronze Age. Iron 
enters to a greater or less extent into all our structures, 
from skyscrapers to dwellings, and from bridges to 
watches; it forms the framework of railroad cars, steam- 
ships and automobiles; it forms the engines of all our 
means of locomotion (Fig. 34). It is the fourth most 
abundant element in the earth; it is present in the sun 
and in the other planets. The magnetism of the earth 
leads us to believe that the interior of the earth is mostly 
iron. Uncombined iron is found in only very small 
amounts in the earth, and this is mostly in meteors which 
have fallen to earth. The ores are very abundant and 
very widely distributed over the earth's surface. The 
usual ores used in smelting iron are the two oxides, hema- 
tite, F<'/).,, and magnetite, Fe 3 4 . The latter is magnetic ; 
that is, it attracts other magnets and iron itself. A huge 
bed of it north of Canada constitutes the magnetic pole 
of the earth, to which all compass needles point. 

Over L2,000 years ago the Greeks and Egyptians ob- 
tained small amounts of iron from its ores and forged it 
into weapons. She Romans, 2,000 years ago, made still 
more use of it. Bui iron has not been an abundant and 
cheap metal for much over 200 years, and it has not been 
used extensively for building purposes for over 50 years. 

112 



SMELTING OF IRON 



113 



Smelting of Iron. — Since iron ores are compounds of 
iron and oxygen, the problem in obtaining the iron is to 
abstract the oxygen from it. We have seen that at high 
temperatures carbon has a strong affinity for oxygen. 
This property is utilized in smelting iron ores. A mixture 
of coke and iron ore is dumped into a large tower of fire- 




Fig. 34. — A typical scene in the Iron Age in which we live. This is a large iron foundry 
housed in a building composed entirely of steel and glass. 

brick called a blast furnace (Fig. 35). Since ore contains 
sand impurities, limestone is also added to the mixture 
as a flux. A blast of hot air is forced into the bottom 
of the furnace ; the coke burns with great heat, combines 
with the oxygen of the ore, the iron which is freed is 
melted by the high temperature, sinks through the tower, 
and collects in a basin at the bottom. The limestone flux 
combines with the sand to form calcium silicate, which 



114 



THE HEAVY METALS 




Lumps of coke Cjt£ 

Lumps of limestone i O 

Lumps of iron ore ■ — % 

Drops of melted iron ■ • f 

Drops of melted slag ■ Q 

Layer of melted slag . r^C^FC 

Layer of melted iron , j g 



' 15 —Diagram of a blasl furnace, where iron is smelted from its ores. Ore, coke, 

and limestone arc fed in at the top, A blasl of highly heated air is blown in at B, which 
the combustion of the coke, the reduction of the ore, and the fusion of the limestone 
nritfa the impurities of the ore to form a slag. The molted iron and slag drop to the bottom 
of the furnace; the iron is drawn off at ('. the slag at /;. The gases escaping at .1 contain 

?i good deal of carbon monoxide; hence they are burned to heat the air blown in at B. 



KINDS OF IRON AND STEEL 115 

melts like glass, drops to the bottom of the tower and 
floats on top of the melted iron. The reactions involved 
are essentially as follows : 

FeA + 2 C = 2 Fe + CO, + CO 

iron ore coke iron carbon dioxide carbon monoxide 

CaC0 3 + Si0 2 == CaSiOg + C0 2 

limestone sand calcium silicate carbon dioxide 

It will be noticed that the gaseons products of the 
reaction are carbon dioxide and carbon monoxide, which 
pass out of the flue at the top. Since the CO is still 
capable of burning and furnishing considerable heat, the 
gases from the flue are brought down and burned to heat 
the air which passes into the furnace as a blast. 

Kinds of Iron and Steel. — The blast furnace is operated 
continuously. Mixed ore, coke and limestone are added at 
the top from time to time, and the melted iron and melted 
slag are drawn off at the bottom through separate taps. 
The iron is run into moulds, and when it hardens it is the 
pig-iron of commerce. This pig-iron, or cast-iron, is used 
directly in castings, such as pipes, the heavy portions of 
machinery, pumps, and similar articles. It is very brittle 
and breaks readily. It is far from being pure iron, con- 
taining considerable carbon, sulfur, and phosphorus. 
When these are mostly removed, and the iron subjected 
to mechanical annealing, the product is wr ought-iron. It 
is very tough, soft, and malleable. When the cast-iron is 
subjected to purification from carbon, sulfur and phos- 
phorus, and then definite amounts of carbon added back 
to it, steel is the result. This is hard and has a crystalline 
structure. Its properties can be greatly modified by treat- 
ment with heat and by the amount of carbon added to it. 
Thus, as a result of special treatments, we can have very 
hard steel for tools and cutting edges, or we can have 
tough, elastic steel for springs and structural girders. 



lit) THE HEAVY METALS 

The properties of steel can be greatly modified by the 
addition of other metals; thus nickel steel is hard and 
elastic, and is used in the armor plate on warships; man- 
ganese steel is extremely hard, and is used for stone- 
crushers, safes, etc.; tungsten steel retains its magnetism 
very well, hence is used for permanent magnets; vana- 
dium steel is tough and elastic and is much used in auto- 
mobile parts. 

Compounds of Iron. — The compounds of iron are numer- 
ous, but are relatively unimportant. The ore discussed 
above, Fe 2 3 , when finely ground, is used as a dark red 
paint pigment under the name of Venetian red or 
red oeli re. 

Iron sulfate, FeS0 4 , also called green vitriol and cop- 
peras, is used for killing weeds, in the dye works, and in 
making writing ink. In the latter, the iron is combined 
with the tannic acid from nutgalls, forming iron t annate, 
which is bluish-black. 

Laundry bluing is a complex compound of iron and 
potassium cyanide. A similar iron cyanide compound is 
used in making blueprint paper. Iron citrate is used as a 
medicine to supply iron to the blood. The red corpuscles 
of blood are composed of a complex compound of iron and 
protein. Its function is to carry oxygen from the lungs 
to the various tissues, where it is used for combustion. 
linn therefore plays a very essential part in animal physi- 
ology. It is also always found in small amounts in plants, 
and is connected with the formation of the green coloring 
matter, chlorophyll. 

Lead. — This metal is seldom found in the uncombined 
state in nature, l>ut usually as the sulfide, PbS, commonly 
called galena. When this is roasted, oxygen combines 
with the sulfur and sets the lead free : 

PbS ; 20 = i>i> | go 



COPPER 117 

Uses of Lead. — About a million tons of lead are annually 
produced in the world. Great quantities of it are used in 
making water pipes. Water containing dissolved air will 
dissolve lead slightly, and the soluble compound formed 
is somewhat poisonous. If, however, the water is at all 
hard, that is if it contains some calcium bicarbonate or 
sulfate, a coating of lead carbonate or lead sulfate is 
formed on the lead pipe which prevents any further dis- 
solving of the metal. Hence it is perfectly safe to use 
lead pipes for drinking water, unless the water is soft. 
Other very important uses of lead are in storage batter- 
ies, babbitt metal, shot, solder, and type metal. The most 
important compound of lead is a carbonate, commonly 
called white lead. It has been the basis of paints for three 
hundred years, and the old Dutch process of making it, 
although slow, still produces a product with the best 
covering power. Briefly, the process consists in allowing 
carbon dioxide and the vapors of acetic acid to act on 
sheets of lead. The lead is suspended over an earthen 
jar of vinegar, which contains the acetic acid, and ferment- 
ing horse manure around the jar furnishes the carbon 
dioxide, and the heat necessary to vaporize the acid and 
the vinegar. The white lead ground with linseed oil forms 
the body of the paint ; to this are added pigments to give 
paints of different colors. Some substitutes and adulter- 
ants of white lead are lead sulfate and barium sulfate, 
which form paints of inferior wearing qualities. Painter's 
sickness is a result of the skin absorbing some of the 
poisonous lead compounds. ' Lead arsenate is a poisonous 
compound used as a cheaper substitute for Paris green 
in killing potato beetles and other chewing insects. 

Copper. — This metal is found in the uncombined state 
in considerable quantities ; this fact, together with the fact 
that it is easily worked into various shapes by hammering, 
is the reason it was one of the earliest metals used by 



! 



THE HEAVY ME" 



man. Copper implements are found in the most ■tenrifamdt. 
I the elL. 1 in and copper kno^sra a* 




rnanirttai 

- 



■ 

mr puppet to-day, banc* 

^ ^' -' ^ulffcfci 






TINWARE 119 

carbonates. Copper is a rather hard and tough metal; 
it can be hammered or rolled into sheets and- drawn into 
wires readily, takes a high polish, and corrodes but slowly 
in the air. For these reasons it is used in vast quantities 
for roofing material, ornamental cornices, electric wires, 
covering the bottom of ships and for coins. 

Copper Alloys. — It forms some of our most important 
alloys, among them being brass, which is copper and zinc; 
German silver, copper, zinc, nickel; bronze, copper and 
tin; our silver and gold coins are one-tenth copper, our 
nickels are three-fourths copper and one-fourth nickel, and 
our pennies contain a little tin and zinc besides the copper. 

Copper sulfate is the best-known compound of copper; 
it is commonly called ' ' blue stone ' ' and ' ' blue vitriol. ' ' Its 
formula is CuS0 4 . It is used in preparing other copper 
compounds, in killing the weeds in ponds, in sterilizing 
swimming-tank water, and in making Bordeaux mixture, 
which is the common spray material used to protect plants 
from fungous diseases (Figs. 36 and 37). 

Tin. — Tin is not found in the free state in nature, but 
usually as the oxide Sn0 2 , from which it is readily freed 
by roasting with coal, as in the smelting of iron. For this 
reason it could be produced even in ancient times and 
was used in connection with copper to produce bronzes. 
The famous tin mines of Cornwall, England, were first 
discovered and worked by the Eomans during their occu- 
pation of England. Besides bronze, tin forms solder and 
pewter when alloyed with lead. 

Tinware. — The greatest use of tin is in coating iron to 
prevent rust and the action of fruit acids. All our tin- 
ware, such as cans, kitchenware, and roofing, is made by 
dipping the iron core into melted tin. The tin itself will 
neither rust nor corrode; but when the thin coating of 
tin is marred, the iron beneath rusts very rapidly. Milk 
cans, separator parts, etc., have very heavy coatings of 



L20 



THE HEAVY METALS 




-Spraying with poisonous compounds of arsenic and lead will largely control these 
Left above, plum curculio with small fruit just attached. Right above, codling 
moth and its effect on apple. Below, potato beetle in different stages on the plant. (Smith's 
Insect Friends and Enemies.) 



COMPOUNDS OF MERCURY 121 

tin which prevent their rusting for a/long time. The prin- 
cipal use for compounds of tin is in the weighting of silk. 

Zinc. — This metal occurs usually as the carbonate and 
the sulfide. The ore is first roasted, then smelted with 
coke or coal. The metal is used in the sheet form for gut- 
ters, roofs, tanks, fancy gabies, and other exposed parts, 
because it corrodes but very slightly in air. When a sheet 
of iron is dipped into melted zinc it receives a coating of 
the zinc. This material is then called galvanized iron. 
Brass is the principal alloy of zinc. Zinc oxide, ZnO, 
is used in huge quantities as a base for paint instead of 
white lead. As it is a mild poison, it is used in ointments 
as an antiseptic. 

Mercury.— The only common metal that is a liquid at 
ordinary temperatures is mercury. It boils at a relatively 
low temperature, at about 500° F. It is used in barome- 
ters and thermometers. Since it freezes to a solid at 
39° F. below zero, alcohol instead of mercury must be 
used in thermometers in cold climates. One of the most 
interesting properties of mercury is that of amalgamation 
with other metals. This is really a dissolving of the 
other metal by the mercury, much as water dissolves 
sugar. The amalgam with which the dentist fills a cavity 
in a tooth consists commonly ox tin, silver, and mercury. 
They are mixed just before using to a stiff paste, which 
hardens to an insoluble substance in a few hours. A tin 
amalgam was formerly used to coat the backs of mirrors. 
In gold and silver mining, the finely-ground ore is ex- 
tracted with mercury; the latter dissolves the particles 
of gold and silver and leaves the quartz and other resi- 
dues behind. 

Compounds of Mercury. — Mercury forms two chlorides : 
mercurous chloride, HgCl, called calomel, is considerably 
used in medicine as a purgative and as a stimulant for the 
secretory organs ; mercuric chloride, HgCl 2 , called corro- 



122 THE HEAVY METALS 

sive sublimate, is a powerful poison, and as such finds 
good use as a disinfectant for surgical instruments and 
the hands of surgeons, for seed-potatoes to kill diseases, 
and for museum specimens. Mercuric fulminate is the 
explosive in percussion caps, used to discharge 
other explosives. 

Silver. — Silver is a white metal, takes a very high 
polish, corrodes rather quickly, especially in atmosphere 
contaminated with sulfur fumes from the burning of soft 
coal, and is softer than copper, but harder than gold. 
For this reason 100 parts of copper are added to 900 of 
silver for use in U. S. coins, jewelry, ornaments, table cut- 
lery, etc; this alloy is coin silver. A current of electricity 
decomposes the salts of silver and deposits a coating of 
silver on one of the electrodes; knives and other objects 
are silver plated by immersing them in this solution and 
causing the silver to be deposited on them. Depending 
upon the thickness of the coat, it is called single, double, 
or triple plated. The backs of mirrors have some silver 
mixed with mercury. For coins and for ornaments, silver 
has been used since earliest times, as it occurs in the un- 
combined state in many places, and hence requires no 
smelting. It was the silver and the gold of the ancient 
Mexicans that attracted the early Spanish voyagers to 
our shores. 

Photography. — One of the most important uses of com- 
I »oii uds of silver is in photography. The photographic film 
or plate is covered with a thin film of gelatin in which is 
suspended a very fine powder of silver bromide, AgBr, or 
silver chloride, AgCl. When the plate is put into a "de- 
veloper," the latter decomposes the silver bromide 
rapidly wherever the light struck it, but very slowly where 
it did not. In the decomposition, black particles of silver 
are deposited. Thus, on developing an exposed plate, the 
parts exposed to the most light will develop black, and 



GOLD 123 

those exposed to the least light will develop gray or 
remain white. This constitutes a "negative," since the 
lighter parts of the object photographed appear dark, 
and the darker parts appear light. On laying a piece of 
photographic paper on the negative and allowing light to 
pass through the latter to the paper, a " positive' ' can be 
developed, as the darker parts of the negative will appear 
as the lighter parts in the paper. The science of photog- 
raphy has developed at an enormously rapid pace during 
the last thirty years. When films could be made which 
were so sensitive as to require only one-hundredth of a 
second exposure to light, pictures of a moving object could 
be taken at the rate of sixteen a second; and when these 
pictures are snown on a screen at the same rate, we have 
our moving picture. 

Since silver compounds are poisonous, a few of them 
are used as disinfectants. ' Argyrol is one of these. 

Gold. — Although interesting enough in a financial way, 
gold is chemically a rather uninteresting element, since it 
is very inert, forming but few compounds, and these being 
of no special importance. Most of the gold in nature is 
uncombined; hence it has been used from the earliest 
times. Because it does react with so few substances, how- 
ever, and does not corrode in air, it finds many valuable 
uses as a protective coating over other metals, especially 
in architectural work, and in lining the vessels in which 
corrosive chemicals are used. Gold is extremely malle- 
able; one grain of it can be beaten into a sheet that 
will cover half a square yard. This is gold leaf or gold 
foil. Since gold is very soft and wears away readily, it is 
alloyed with copper for most purposes. In jewelry, pure 
gold is called 24-carat; 16-carat gold means 16 parts of 
gold alloyed with 8 parts of copper. Due to new processes 
of obtaining gold from its ores, the production of this 
metal has increased very rapidly during the last few dec- 



124 



THE HEAVY METALS 



ades; as a result it has become much more plentiful. 
However, since gold is our standard of value, instead 
of saying that gold has become cheaper, we say that other 
commodities have become more expensive. 

Platinum. — This is a silvery-white metal, very resistant 
to the action of most chemicals. For this reason it is much 
used as the lining of machinery employed in making nitric, 



Table VIII 

Summary of the Properties of the Heavy Metals 



Metal 


Where found and in what 
principal form 


Uses of the metal and its compounds 


Iron 


As Fe 2 3 , hematite 


Fe — most important of all metals indus- 




As Fe 3 4 , magnetite 


trially; used as wrought-iron, cast-iron, 
and steel. 

IV>n 4 — killing weeds; in dyeing; in mak- 
ing ink. 

Fe 2 3 — paint pigment. 

Iron is ;m essential element in both plant 
and animal life; occurs in red blood 










corpuscles. 


Lead 


As PbS, galena 


Pb — used for water pipes and in batteries; 
in alloy-, as babbitt and solder. 

PbS0 4 — paint pigment. 

Pb(OH) 2 .2PbC0 3 — white lead, paint pig- 
ment. 


Copper 


Found in large quan- 


Cu — used for electric wire, roofs, in many 
alloys, as coins, brass, bronze, gun-metal 




tities as Cu 




AsCuS 


C11SO4 — insect poison. 


Tin 


AsSn0 2 


Sn — used in tin plating; in alloys, as 
bronze, solder, pewter. 


Zinc 


As ZnC0 3 and ZnS 


Zn — used in galvanizing iron; in batteries; 

in alloys, as brass. 
ZnO — paint pigment; medicine. 


Mercury. . . 


AsHgS 


Hg — used in thermometers and barometers. 
HgCl — calomel; medicine. 
HgCb — corrosive sublimate; poison, dis- 
infectant. 


Silver 


As Ag and AgS 


Ag — used for coins, jewelry, plating. 
AgCl and AgBr — photographic plates and 


Gold 


As Au 


Au — used for coins and jewelry. 
Xo important compounds. 


Platinum . . 


AsPt 


Pt — used in jewelry and electrical instru- 
ments. 
Xo important compounds. 



<v- 



LABORATORY EXPERIMENTS 125 

sulfuric, and other strong acids. It is used in jewelry for 
Betting gems, as it is hard, tough, and non-corrosive; 

and as the contact points of electrical instruments, be- 
cause it is not oxidized by the sparks. It is our heaviest 
metal, being 21.47 times as heavy as water. Like gold, 
its compounds are rare and uiimportant. It is our most 
costly metal. 

QUESTIONS 

1. Why was iron not much used by the ancients? 

-. Besides abundant iron ore, what other natural product must be cheap 
and abundant before iron can become cheap? 

3. Describe the chemistry of the blast furnace, including both the iron 

and the slag. 

4. What are the chemical differences between wrought- iron, cast-iron and 

steel ? 

5. Name some important alloys of iron. 

(i. Name five compounds of iron and state their uses. 
7. Why is it safer to use lead pipes with hard water than with soft? 
S. What is white lead, and how is it made? 

9. State three ways in which the poisonous properties of lead and its 
compounds may become important. 

10. Why could copper, tin, gold, and silver be utilized by man from the 

earliest times? 

1 1. What use is made of the poisonous nature of copper compounds? 

12. Why are zinc, tin, and silver used to plate iron? 

13. What is bronze? Solder? Dentist amalgam? Sterling silver? Brass? 

Galvanized iron? 

14. What is calomel? Corrosive sublimate? Blue stone? Chlorophyll? 

15. Describe the chemistry involved in making a photograph. 

LABORATORY EXPERIMENTS 

39. To Show the Chemistry of Iron Rust. — Force a wad of steel wool 
or a muslin bag full of iron filings into a large test tube or graduated cyl- 
inder so that it remains suspended half way. Pour water into the tube to 
the depth of an inch, wetting the iron. Invert the tube in a dish containing 
about an inch of water, and support it by means of a clamp. Allow to stand 
for a few days, noting any change in the level of the water inside the tube, 
and any temperature effect on the tube near the mass of iron. If the water 
)i>» > an inch or more in the tube, remove the latter and test the air in it 
with a glowing splinter. What kind of a chemical change is the rusting of 
iron? Why does painting prevent iron from rusting? 

40. To Reduce Copper From an Ore. — Grind together equal volumes 
of copper oxide and charcoal. Place the mixture in a test tube. Clamp the 
tube in an almost horizontal position, so as to spread out the mixture in a 
thin layer. Carefully heat, at first gently, then as hot as the tube will 



126 THE HEAVY METALS 

stand, for several minutes. A wing-top burner is best. Cool, and note the 
appearance of the mixture. What has been formed ? 

CuO + C = Cu + CO 

copper oxide carbon copper carbon 

monoxide 

This same method is used for the reduction of many ores, especially iron. 
Coke is the usual form of carbon. What use is made of the CO? (Fig. 35). 
41. To Reduce Mercury From an Ore. — Heat some mercuric acid in a 
test tube. Note the drops of metallic mercury that form on the sides of 
the tube. 

HgO = Hg + O 

Test for any increased amount of oxygen in the air in the tube. 

42. To Show the Reduction of Silver Nitrate by Sunlight. — (a) 
Moisten a strip of filter paper with a solution of silver nitrate, then expose 
to direct sunlight. What is the dark substance formed? What great use is 
made of this property of silver Baits? 

(b) In what different ways <an metals be separated from their com- 
pounds as illustrated by the last three experiments? 



CHAPTER X 

SOME COMMON NON-METALS 

Significance of Metals and Non-metals. — We have seen 
in the preceding chapter that among the metallic chemical 
elements are some of our most important substances in 
everyday use. Many of the metals that we discussed, 
such as sodium, calcium and potassium, are not used as 
metals, but their compounds are of the utmost necessity 
not only to processes outside of our body, but to our 
very life processes themselves. Other metals, as gold and 
platinum, find practically all their usefulness as elements 
and none as compounds. Copper, iron, and lead are im- 
portant both as elements and in compounds. 

It may have been noticed that most of the compounds 
of the metals were salts ; that is, the metal had replaced 
the hydrogen of an acid to form a salt. If the reader 
looks back through the last two chapters at the various 
salts discussed, it will be noticed that the majority of 
the salts are chlorides, sulfates, nitrates, phosphates and 
carbonates. That is, there are about half a dozen acids 
that form the most important salts with all metals. The 
significance of that is this : the non-metallic elements 
always form the acid radicles ; the non-metallic elements 
involved in the above salts are, of course, CI, S, N, P, 
and C; therefore, since their salts appear to constitute 
the important compounds of the metals, these non-metals 
should now occupy our attention. 

Hydrogen and Oxygen as Non-metals. — Besides the five 
non-metallic elements just mentioned, we have already 
discussed hydrogen and oxygen. It might be well to point 
out here that these two non-metals are an exception to 

127 



128 SOME COMMON NON-METALS 

the statement that the non-metals form acid radicles. 
Oxygen may be a part of the radicle, as in the sulfate 
radicle, -S0 4 ; but in the chlorides and iodides it is not. 
Oxygen is never the radicle itself. Hydrogen is the char- 
acteristic element of all acids ; it is the presence or absence 
of a hydrogen replaceable by a metal that determines 
whether or not a compound is an acid. The fact that 
hydrogen and oxygen do not form acid radicles of their 
own is not the important tiling, however; the fact of 
greatest importance is, that hydrogen is present in all 
acids, that the OH group is present in all alkalies, and 
that whenever a salt is formed the hydrogen and the OH 
always form water. Thus we can consider the non-metals, 
hydrogen and oxygen, as being in a class by themselves. 
They are certainly not metals, for they are gases; but, 
nevertheless, they do not form acids as other non-metals. 

We can see, then, that the study of a non-metal involves 
first, the study of the element alone; second, the acid or 
acids which it forms; and third, the salts of these acids. 
In some cases there are important oxides as well; but 
the oxides, as we shall see, are one phase of the acids. 

The most important and commonly occurring non- 
metallic elements are hydrogen, oxygen, nitrogen, carbon, 
sulfur, phosphorus, chlorine, and silicon. To this might 
be added the less important elements, iodine and arsenic. 

Nitrogen. — Nitrogen, as we have seen, is the chief gas 
of the air. It is inactive there, not combining with other 
elements under ordinary circumstances, and not being 
utilized by plants or animals, with the exception of the 
legumes. Under the influence of an electric discharge, 
such as lightning, nitrogen and oxygen combine to form 
an oxide, which dissolves in the descending rain water to 
form nitric acid, HXO :J : 

2N +50 = xo. 
NA + HX) = 2HN0 3 



AMMONIA L29 

This is one of the ways in which nitric acid is formed in 
nature; the most important way, in the soil, we shall con- 
sider in a later chanter. 

Nitric Acid. — This is the most important acid which 
nitrogen forms; it forms salts with practically all metals, 
some of which are of greal importance. In the soil, nitric 
acid exists as the nitrates of sodium, potassium, calcium, 
and magnesium. Two of our commonest nitrogenous fer- 
tilizers are sodium nitrate (Chile saltpeter) and calcium 
nitrate. The latter is made artificially, as we have seen, 
by an electrical process. Since all nitrates are very solu- 
ble in water, they are easily leached out of soils; this is 
the reason why there is seldom any considerable accumu- 
lation of them in soils, and why nitrate fertilizers are not 
added once in several years, but several times in one year, 
in small amounts, so that the plants can use them up 
before they are leached out. 

Potassium nitrate, KN0 3 , is commonly used in gun- 
powder and in fireworks; it finds some use also in the 
curing of meat, as in dried beef and corn beef. 

Ammonia. — One of the most remarkable facts about the 
chemistry of nitrogen is that with oxygen it forms a strong 
acid, and that with hydrogen it forms an alkali. The lat- 
ter is ammonia, NH :5 ; it can be made artificially, and it is 
always formed when manure ferments ; but practically all 
of our commercial ammonia is a by-product of the coal-gas 
works. Ammonia is an invisible gas, but it has a very 
penetrating, biting odor. It is soluble in water to such an 
extent that one quart of water will dissolve 700 quarts of 
ammonia gas. This water solution is our ordinary house- 
hold ammonia water, or ' ' aqua ammonia, ' ' or ' ' spirits of 
hartshorn. ' ' A chemical reaction really takes place when 
the gas dissolves in water : 

NH 3 + H s O = NH.OH 



L30 SOME COMMON NON-METALS 

This compound, ammonium hydrate, shows the typically 
alkaline characters of hydrates: it turns litmus paper 
blue, and neutralizes acids, forming ammonium salts and 
water in a way exactly analogous to that of the hydrates 
of metals : 

NII.WII + HC1 = H.O + NH 4 C1 (ammonium 

chloride ) 
Na OTT + HC1 = H,0 + NaCl (sodium 

chloride) 
2X11,011 + TLSO, = 2H,0 + (NH*)aS(X (ammonium 

sulfate) 
2NaOTI + H,S() + — 2 H,0 + Na..SO, (sodium 

sulfate ) 

Some of these ammonium salts are of great practical 
importance. Ammonium sulfate is one of our commonest 
nitrogenous fertilizers ; ammonium chloride, sal-ammo- 
niac, is much used in electric batteries, in medicine, and 
in dye-works. The old-fashioned smelling-salts were am- 
monium carbonate. This compound gradually breaks 
down into ammonia: 

(N'll,ii O, = NH S + NH,HCO., ( ammonium bicarbonate ) 

The inhaled ammonia gas exerts a mildly stimulative effect 
on the nerves. 

Refrigeration with Ammonia. — Ammonia gas can be 
readily liquefied by pressure in steel cylinders. When the 
compressed gas is allowed to escape into a chamber and 
expand, it absorbs a great amount of heat, reducing the 
temperature of the chamber very considerably. This 
phenomenon is utilized in refrigerating plants and arti- 
ficial ice factories (Fig. 38). The cooling chamber is a 
series of tubes surrounded by strong brine. The brine 
becomes very cold, far below the freezing-point of water, 
without itself freezing. This cold brine is circulated 
around small tanks of water, and the water gradually 
freezes to ice. Or the brine is piped around the walls 



EXPLOSIVES 



131 



of cold-storage rooms to cool the air. The expanded 
ammonia gas is again liquefied, and thus is used over 
and over again. 

Explosives. — A very noteworthy characteristic of many 
compounds of nitrogen is that they decompose when 




Fig. 38. — Scene in a refrigerator room of a large packing house. Bacteria cannot thrive at 
low temperatures; hence cold storage is a very effective means of preservation of meat, eggs, 
dairy products and fruit. The cold is produced by compressing ammonia gas with the ma- 
chines shown here, then allowing the gas to expand in chambers surrounded by brine. The 
expansion cools the gas, which cools the brine, which is then piped to the cold storage rooms. 

jarred or ignited, and liberate large volumes of gaseous 
products. These unstable compounds are our high ex- 
plosives. Some of them are nitroglycerin, nitrocellulose 
(gun-cotton or smokeless powder), and trinitrotoluol 
(the famous T. N. T. of the World War). Celluloid and 
collodion are near chemical relatives to nitrocellulose. 



132 ME >MMON NON-METALS 

Nitrogen in Living Celis. — \Ve shall have occasion in 
later chapters to discuss the relation of nitrogen com- 
pounds to living- animals and plants. Nitrogen compounds 
constitute the living material of all plant and animal cells. 
This is such an all-important subject that it demands 
special attention. 

Carbonates. — The next non-metallic element, carbon, 
we have already discussed at some length. \Ve saw that as 
an element it is our most important solid fuel; that com- 
bined with hydrogen it forms our principal liquid and 
gaseous fuels ; that combined with hydrogen and oxygen 
it forms thousands of different compounds; that it has 
two important oxides, the monoxide and the dioxide ; that 
the latter occurs in small amounts in the air, and fur- 
nishes all green plants with their source of carbon; that 
enormous amounts of carbon dioxide are held in the earth 
in the form of limestone. 

( arbon dioxide, when dissolved in water, forms a 
solution that has a slightly sour taste, and will gradually 
redden litmus paper. It must therefore form an acid : 

C0 2 + H\0 = H 2 C0 3 (carbonic acid) 

It is not a very well-defined acid, but it does form a series 
of salts with many metals. These salts are the carbonates. 
We have already mentioned the carbonates of sodium, 
potassium, calcium, magnesium, and of several heavy 
metal-. We have seen that sodium carbonate, Xa 2 CO : >, 
Is our sal-soda, or washing soda; that sodium bicarbonate, 
NaHCO ., Lfi our baking soda or saleratus; that calcium 
carbonate occurs as limestone, marble, and chalk; that 
potassium carbonate is the form of potash in wood ashes. 
We have also emphasized a very important chemical reac- 
tion which all carbonates show, and that is that they give 
off carbon dioxide when treated with an acid. In order to 



SULFUR 133 

understand the full significance of this reaction, let us take, 
for example, sodium carbonate and hydrochloric acid: 

Xa 2 C0 3 + 2HC1 = 2XaCl + H 2 + CO, 

We start with a strong acid; the products formed are 
common salt, water, and carbon dioxide, which escapes 
as a gas. In other words, we destroyed an acid, and have 
left only a neutral salt. That is, the carbonate in reality 
neutralized the acid. Thus, if we have some vinegar, and 
carefully add baking soda to it, the soda, being a car- 
bonate, will react with the acetic acid of the vinegar, and 
carbon dioxide gas will bubble up out of the vinegar and 
escape into the air. If we add just enough soda, all of 
the acid and ail of the soda will be destroyed, and there will 
be left behind a neutral vinegar, containing a little sodium 
acetate, a salt, in solution : 

HC 2 H 3 0, + XaHC0 3 = NaC 2 H 3 2 +H 2 + C0 2 

acetic acid baking soda sodium acetate water carbon dioxide 

Carbonates thus apparently constitute a special form 
of alkali, since they neutralize acids to form salts and 
water. The keynote to the whole reaction is simply the 
fact that carbon dioxide is always formed ; this is a weak 
acid, and thus takes the place of the acid neutralized ; and 
as it is a gas, it escapes and removes itself from the 
reacting substances entirely. There are many places 
where carbonates are used to neutralize acidity : in cook- 
ing with sour milk or molasses, baking soda is used; when 
a soil becomes acid, limestone is added to it ; in the preser- 
vation of certain fruit juices and in the manufacture of 
some sugar products from acid juices, limestone is 
often used. 

Sulfur. — This is probably one of the oldest-known 
chemical elements. It is mentioned often in the Bible, 



i:;i - >ME O >MMON NON-METALS 

usually being called "brimstone." In some way or other 
the choking fumes of burning sulfur suggested that the 
tires of Hades must be concerned with this substance, and 
hence brimstone has always been coupled with Hades in 
the superstitious mind. Sulfur is found as the element 
in many places in the earth, especially in volcanic regions. 
In the Japan Archipelago there are whole islands of fairly 
pure sulfur; in Sicily, Spain, California, Mexico, and 
Yellowstone Park, there are large deposits of sulfur that 
no doubt had their origin in volcanoes. In Texas and 
Louisiana there are immense beds of sulfur, several hun- 
dred feet below the ground, that had an entirely different 
origin. There are certain bacteria and alga? which decom- 
pose sulfates as gypsum, CaS0 4 , and deposit minute 
granules of sulfur in their cells. After the death and the 
decay of the cells, the sulfur granules are left, and grad- 
ually accumulate in beds, similar to the formation of lime- 
stone beds. These sulfur beds thus furnish another 
interesting connecting link between the organic or living 
world and the inorganic or mineral world. 

Commercial Sulfur. — The mining of sulfur when it 
occurs above ground offers no more difficulties than the 
digging of sand. In this country, however, most of the 
sulfur comes from the underground beds of Texas and 
Louisiana and a very neat bit of chemical engineering is 
involved in obtaining this sulfur (Fig. 39). Instead of 
mining it like coal, a far cheaper method is used, consist- 
in-- of melting the sulfur by superheated steam and then 
pumping the liquid sulfur to the surface. As sulfur melts 
at about 245 E\, it is easily melted by the steam. The 
molten sulfur LS poured into moulds to solidity, or into 
huge tanks from which the solid sulfur is removed by 
blasting. In this form it is called commercially "roll- 
Bulfur" or "brimstone." At a high temperature sulfur 
boils; if the vapors are cooled and condensed on the sides 



USES OF SULFUR 



135 



of brick vaults, they form a finely-powdered, crystalline 
sulfur called ' ' flowers of sulfur. ' ' 

Uses of Sulfur.-— Something like half a million tons of 
sulfur are used in the United States every year. Both the 
element and its compounds are important. Flowers of 




Fig. 39. — Texas sulfur wells. A hole is drilled down into the bed cf suKur, and a double 
pipe, one within the other, is let down the hole. Live steam is passed into the sulfur through 
the inner tube; the sulfur is melted and forced to the surface of the ground through the 
outer tube. It is pumped into huge vats, shown in the picture, where it cools, and is then 
ready for market. (Union Sulfur Co.) 

sulfur form one of the constituents of black gunpowder ; 
they are commonly found in veterinary patent medicines ; 
they are sometimes used in poultices in human medicine ; 
and they are used very considerably in the vulcanizing 
of rubber. When it is burned, sulfur dioxide is formed. 



S + 20 



so 2 



136 SOME COMMON NON-METALS 

This is an acrid, biting, choking gas. It has two very 
valuable properties, its bleaching action and its germicidal 
effect. Immense quantities are used in bleaching straw, 
paper, linen, dried fruits, molasses, and other products. 
A- a disinfectant it is often burned in chicken houses, 
barns, and residences to kill disease germs and insect 
pests. Sulfur dioxide gas is now compressed into steel 
cylinders for use in disinfecting and bleaching. Another 
use of sulfur is in the combination of slaked lime and 
sulfur, called " lime- sulfur, ' ' used as a dip for sheep and 
hogs, and for killing scale insects on trees. 

The King of Chemicals. — By far the greatest use of 
sulfur is in the manufacture of sulfuric acid, H 2 S0 4 . This 
acid is not in itself of such great importance; but there 
is hardly a chemical industry of any sort which does 
not utilize sulfuric acid at least indirectly to prepare its 
products. We have already seen that hydrochloric and 
nitric acids are prepared from their salts by means of 
sulfuric acid; it is the mechanism by which nitric acid 
is made to combine with glycerin, cotton, and toluol in 
producing our high explosives; it is used in coal-gas 
factories for washing the ammonia from the gas; our 
acid phosphate fertilizers are formed by the action of 
sulfuric acid on bones or rock phosphate ; the manufacture 
of most of our drugs, dyes, cosmetics, pure metals, and 
hosts of other commodities, involves the use of sulfuric 
acid somewhere in the processes. Because of this extra- 
ordinary usefulness, sulfuric acid is often termed "the 
king of chemicals." 

Sulfides and Sulfates. — Sulfur occurs very commonly 
in nature combined with metals as sulfides. Fools' gold 
is a sulfide of iron; the principal zinc and tin ores are 
sulfides. Tin- Baits of sulfuric acid are also rather abun- 
dant. Potassium and magnesium sulfates are found in 



YELLOW AND RED PHOSPHORUS 137 

the Stassfurt potash mines ; magnesium sulfate, we have 
seen, is a common constituent of so-called alkali' waters; 
there is some sodium sulfate in ocean waters; the ala- 
baster of Biblical literature is a certain form of calcium 
sulfate. Sulfur compounds are found in all soils, and in 
all animals and plants. In fact, it is one of the necessary 
elements for life processes, both plant and animal. 

When eggs decay, the peculiarly offensive odor is due 
to hydrogen sulfide, H 2 S. The characteristic odor of mus- 
tard, onion, garlic, and cabbage is due to certain organic 
compounds of sulfur. One of the most vicious gases used 
by the Germans in the World War is called "mustard 
gas"; it is a very poisonous compound of sulfur, but 
it is not the compound occurring naturally in mustard. 

Phosphorus. — This non-metallic element does not occur 
in nature as an element. The reason for this is apparent 
when a piece of phosphorus is exposed to the air; it imme- 
diately begins to fume, showing that it is slowly oxidizing. 
We have all rubbed match-heads in the dark, and watched 
them fume and glow ; this is due to the fact that there is 
phosphorus in the head, and that the rubbing of it exposes 
fresh phosphorus to the air. Certain bacteria emit a 
dim light which is similar to the glow of phosphorus; 
hence the name of " phosphorescence " applied to this 
light, although phosphorus is not involved in the bacterial 
process, any more than it is in the light of fireflies and 
of glow-worms. 

Practically all the phosphorus in nature exists as 
calcium phosphate, either in rock phosphate or in the 
mineral apatite, which is found in granite rocks and in all 
soils. It is not abundant in soils, however, and as grow- 
ing plants require considerable amounts of it, phosphorus 
fertilizers are very much in demand. 

Yellow and Red Phosphorus. — There is one peculiarity 
about phosphorus that makes it unique among all other 



138 SOME COMMON NON-METALS 

elements, and that is that elemental phosphorus exists in 
two forms. The ordinary phosphorus is a yellow, wax- 
like, semi-transparent solid. When it is heated to a 
certain temperature away from air it is converted into a 
brick-red solid. This red substance is still uncombined 
phosphorus, but it now has entirely different properties 
from what it had before. The yello-w phosphorus catches 
on fire at about 100 3 P.; the red at about 400° F. The 
red does not glow in the dark. Yellow phosphorus is 
exceedingly poisonous, while the red is not. The yellow 
dissolves in ether, the red does not. 

Uses of Phosphorus. — Yellow phosphorus is used in 
some rat poisons. These are dangerous to use around 
buildings, however, as the phosphorus very often ignites 
in warm weather, and starts a' conflagration. 

Matches. — The most important use of phosphorus is 
in matches. Advantage is taken of the fact that phos- 
phorus catches on fire at such a low temperature that the 
heat of friction will ignite it. The head of the match 
consists of (1) phosphorus, which does the initial igniting; 
(2) potassium chlorate, which readily liberates large 
amounts of oxygen to continue the burning started by the 
phosphorus; (3) fine sand, clay, or powdered glass to 
increase the friction; and (4) glue, to bind these materials 
into a solid head. Scratching on any surface will ignite 
these matches. Double-dip matches have phosphorus only 
ob the point, thus lessening the danger of their being 
ignited by accident. A still further improvement is the 
safety match, which bears no phosphorus on the head; 
it is ignited by scratching on the side of the box, where 
the phosphorus and powdered glass are glued. Formerly 
yellow phosphorus was the form used, as it ignites more 
readily. The poisoning of workers in match factories, as 
well as of children who accidentally chewed the heads of 
the matches, has broughl about legislation in most coun- 



PHOSPHATES 



139 



tries which demands the use of the non-poisonous 
red variety. 

Phosphates. — Practically the only compounds of phos- 
phorus which are of importance are the salts of phos- 
phoric acid, which has the formula H 3 P0 4 . We saw on 




Fig. 40. — Apparatus for the preparation of nitric acid. 

page 84 how this acid is formed when the fumes of burned 
phosphorus dissolve in water. 

The calcium salt, Ca 3 (P0 4 ) 2 , is found in large quanti- 
ties as rock phosphate, or "floats," in our Southern 
States, and is our largest source of phosphate fertilizer. 
A great deal of it is converted into "acid phosphate," 
CaH 4 (P0 4 ) 2 , which is used as a soluble phosphate ferti- 



140 - mi: o immi >n x< -x-metals 

lizer. and in the purification of juices in sugar manufac- 
ture. The bones of animal bodies consist almost entirely 
alcium phosphate, which fact suggests the possible 
origin oi the rock phosphate beds. 

Chlorine. — This gaseous element does not occur in 
nature as the element but is very abundant in the earth in 
the form of chlorides. The abundance of sodium chloride 
in the earth and in the sea has been mentioned before: 
calcium, potassium, and magnesium chlorides are also 
important in th< SI ssfurt mines. The element chlorine 
_ enish-yellov gas, idingiy irritating to the 

mucous membrane of the nose and throat, causing severe 
"chlorine colds." In even small amounts it is very 
- nous. I toe of the first materials used by the Ger- 
mans when they commenced their gas warfare was chlo- 
rine. The Bufferings of the attacked soldiers were terrible. 
The gas masks devised as a protection against the chlorine 
contained various chemicals which converted the chlorine 
into harmless salts. The principal uses of chlorine are 
in bleaching cotton, straw, linen, and other materials. 
and ae lis ant in water. For these uses, either 

the element itself stored in steel cylinders, or the com- 
• 1 called "hypochlorite" or "bleaching powder," 
s 3 IPig. 7). 

Compounds of chlorine arc found in all plant bodies. 

although it > blynotan< — there. In 

animal b . it is necessary, as the acid of 

ach ju.. a ric acid, UGL This is the 

"muriatic acid" of the tim ,ua ina Lering. 

Silicon.— ( >ur interest in the Is s <' is 

mainly . n their very abundant occurrence in 

eighl • arth being 
S '_■ Thia subsl constitutes all of 

si other 



OXIDES AND NON-METALS 



141 



rocks except limestone. The silicates have rather complex 
formulas. We shall simply mention that some of the 
more useful silicates are talc, pumice, and asbestos; that 
the aluminum silicates constitute all our clays; that 
Portland cement is a mixture of 
lime and aluminum silicate; and 
that "water-glass" for preserv- 
ing eggs is sodium silicate. 

Arsenic and Iodine. — There are 
two other non-metallic elements 
that have important special uses. 
These are arsenic and iodine. The 
first is a very poisonous element 
in all its compounds; hence it is 
utilized in most of our insect and 
vermin poisons, such as Paris 
green, white arsenic, lead arsenate, 
and calcium arsenate. Iodine as 
an element is a good disinfectant; 
it kills germs readily, but is not 
irritating or caustic to raw flesh. 
In wounds, on bruises, and on ton- 
sils it is very effective. In the form 
of potassium iodide it is often 
taken as a medicine, especially for 
goitre. The compound called iodo- 
form is a common disinfectant. 

Oxides and Non-metals. — In our 
discussion of the kinds of com- 
pounds that are formed by the non- 
metals On page 128 We mentioned FlG - 41.— Apparatus for the prep- 
,-. ,,, -1 • t -1 -, , aration of ammonia. 

that although acids and salts were 

the principal ones, some oxides were also important. Let 
us now see exactly the relation which oxides bear to acids. 
For example, let us take a few of the non-metals, and, in 




142 SOME COMMON NON-METALS 

equations, show how they form oxides, and then how these 
oxides unite with water. 

C +20 = C0 2 



CO, 


+ 


H,0 


= ILCOjj (carbonic acid) 


2 P 


+ 


5 


= PA 


I'd 


+ 


3 HX> 


= 2H 3 P0 4 (phosphoric acid) 


s 


+ 


3 


= so a 


so 3 


+ 


H 2 


= H 2 S0.j (sulfuric acid) 



It will be seen that the oxides of the non-metals combine 
with water to form the corresponding acids. This fact 
has its important applications. For example, if sulfur 
dioxide gas, S0 2 , is being used as a bleaching agent, the 
material to be bleached must be moist, since the bleaching 
effect is caused bysulfurous acid, formed thus : 

S0 2 + H 2 = H 2 S0 3 (sulfurous acid) 

Again, when our soft drinks are charged with carbon 
dioxide, the drinks have a sour taste because the carbon 
dioxide forms carbonic acid with the water. 

QUESTIONS 

1. What is the most important characteristic distinguishing metals from 

non-metals? 

2. Name the non-metallic elements we have studied, and state which of 

them form important acids. 
'{. Explain the relation of hydrogen and oxygen to acids and alkalies. 
\. Name the six most important compounds of nitrogen, and give the use 

of each. 
•">. Explain the action of a carbonate in neutralizing an acid. 
ti. \\ hat i> carbonic acid? Name three of its important salts, and give the 

usee of each. 
7. Explain in what ways deposits of carbon and of sulfur in the earth 

form the connecting link between the organic and the inorganic world. 
s ESxplain the important uses of elemental sulfur. 
!». What are some of the most common uses of sulfur in the industries? 

( >n the farm ? 
10. Explain the chemistry of a safety match. 
I I. W hat i- the most abundant compound of phosphorus in our bodies? 

12. What is chlorine gas good for ? 

13. Nana- -(.in., chlorfdee and gire their uses. 

II- What i- th<- in. .-i abundant element in the earth? The most abundant 

compound I 
18 What i- Portland cement? Water-glass? Paris green? 
Hi. Explain the relation between the oxides <»f the non-metals and the acids 

"i i liese elements. 



Table IX — Summary of the Properties of the Non-metals 



Element 



Where found and in what 
form 



Uses of the element and its compounds 



Hydrogen. 

Oxygen. . . . 
Nitrogen. . 

Carbon 
Sulfur 



Phosphorus 
Chlorine. . . 

Silicon .... 

Arsenic. . . . 
Iodine 



Principally in H2O 



As O in air • 

As oxide of a great many 

elements in nature 
As N in air 
Compounds of N very 

scarce in nature 



(See end of Chapter VI.) 

In great quantities as the 

element 
As FeS 2 , pyrites, or 

"fool's gold" 
As K 2 S0 4 and MgS0 4 in 

the Stassfurt mines 



As Ca 3 (P0 4 ) 2 , rock phos- 
phate 



PrincipaUy as NaCl, KCL 

and MgCl 2 
In sea-water and in all 

soils 



As Si0 2 to the extent of 
three-fourths of the 
earth's crust 



In connection with cop- 
per and zinc ores 

In sea-weeds 



H is used for welding; for filling 

balloons. 
H is a constituent of all acids. 
Enters into large number of important 

compounds. 
O supports combustion. 
Compounds too numerous to mention. 

N dilutes the oxygen of the air. 
NH 3 — fertilizer; cleaning agent. 
HNO3 — the acid of many important 

nitrates, as NaN0 3 , KN0 3 , Ca(N0 3 ) 2 
Most explosives are compounds of N. 
All plants and animal cells contain 

compounds of N. 



S — used in medicine; in vulcanizing 
rubber; in gunpowder. 

S0 2 — bleaching straw, sugar cane juice, 
and fabrics; disinfecting. 

H 2 S0 4 is the most important single 
chemical manufactured; in the mak- 
ing of explosives, fertilizers, dyes, 
drugs, and many other commodities. 

Compounds of S are essential to both 
plant and animal life. 

P — used in match-heads; in rat poisons. 

Bones consist of Ca 3 (P0 4 ) 2 . 

Na 2 HP0 4 used in medicine. 

Compounds of P are essential to both 
plant and animal life. 

CI — used in bleaching; in disinfecting 
water. 

CaOCl 2 — bleaching powder. 

HC1 — in the stomach; is muriatic acid. 

NaCl — most abundant compound of CI. 

Compounds of CI are essential to ani- 
mal but not to plant life. 

Si — no important uses. 

Si0 2 — sand; found in most rocks and 
minerals. 

Talc, mica, asbestos, pumice are com- 
plex sihcates. 

Portland cement is aluminum silicate. 

Water glass is sodium silicate. 

As 2 3 - white arsenic; insect poisons 
and sprays; in the manufacture of 
Faris green and lead arsenate. 

I — used as disinfectant. 

CHI3 — iodoform ; disinfectant. 



144 SOME COMMON NON-METALS 

LABORATORY EXPERIMENTS 

43. To Prepare Nitric Acid.— (To be clone by instructor.) Set up the 
apparatus shown in figure 40. using a rubber stopper. A glass retort is 
preferable, as the acid quickly attacks the rubber. The receiving test tube 
stands in cold water. Place 25 g. sodium nitrate in the flask, then add 
14 cc oi concentrated sulfuric acid and fit in the stopper. Gently mix 
the content-, and then carefully heat with a low flame over the nitric acid. 
Save for experiment 44. 

2NaNO, + H,S0 4 = 2 HX0 3 + Na,SO, 

44. To Study the Properties of Nitric Acid. — Use the acid prepared in 
experiment 43, or that in the reagent bottle. 

la 1 Test it with litmus paper. 

lb 1 Dilute a little with water, and add a carbonate. 

(c) Add a few drops of the concentrated acid to wool, finger-nail clip- 
pings, t^ white, and other forms of animal tissues. This yellow color is 
characteristic of the nitrogenous substances called proteins. - 

(d > Into one test tube put a few cc. of nitric acid diluted with an equal 
volume of water: into another put some diluted sulfuric acid; into another, 
hydrochloric acid. Then add a small piece of copper wire to each tube, and 
warm gently. Test any evolved gas for hydrogen. Compare the results with 
in experiment 12. Do all metals displace the hydrogen from acids? 
What gas is evolved from nitric acid by the copper (see equation below) ? 
To what i^ the blue color due? 

3Cu -f 8HNO, = 3Cu(X0 3 «, + 4 H,0 + 2X0 

45. To Prepare Ammonia. — Set up the apparatus shown in figure 41. 
Place H» g. ammonium chloride. 10 g. powdered quicklime, and 20 cc. water 
in the flask. Heat gently, filling two bottles and a test tube with the gas. 
keeping the bottles bottom up on the table. Equation. 

(a) Bel the inverted test tube full of ammonia into a beaker of water. 
Why does the water rise in the tube? What is ammonia water? 

(hi Hold moist strips of litmus paper in one of the bottles. What does 
this Bho* ! 

Moisten a glass rod with concentrated hydrochloric acid, then hold 
it over ;i bottle of ammonia. What are the white fumes? 

Mi + HC1 = XH,C1 

46. To Study the Properties of Sulfur Dioxide. — (a) What was 
ed concerning the chemistry of sulfur dioxide in experiment 0? Write 

.••jiiat i..n- showing the formation of Bulfur dioxide. 

Suspend a piece of wet colored calico, some moist straw, and a 
pink flower m a large inverted bottle; Set the bottle over a 2 g. heap of 
burning sulfur on ;« sheet of asbestos or on a Bhallow iron plate. Examine 
the next day. Fur what is Bulfur dioxide used commercially? How is 
it bandied! 

47. To Study the Properties of Sulfuric Acid. — (a) Prepare a 10 per 
■••lit solution "t ralfuric acid carefully pouring :i <-.< of concen- 

lUlfuric acid int.. i:. <•..•. of water in a beaker. Bv means of a fine 



LABORATORY EXPERIMENTS 145 

glass rod write on a piece of paper with the acid, and dry over a flame. To 
what is the brown coloration due ? 

(b)Pour some concentrated sulfuric acid into a little moist sugar in a 
beaker. The beaker should stand on a large sheet of paper. What is the 
black substance? 

(c) Test the solubility of sulfates of Na, K, Mg, Ca, Cu and Fe, by the 
method used in experiment 13. To a dilute solution of one of the sulfates 
add a little hydrochloric acid, then a few drops of BaCL solution. 

Na.SC), + BaCL = BaS0 4 + 2 NaCl 

The precipitate is barium sulfate, BaS0 4 . This is a commonly used test 
for sulfates. 

48. To Study Phosphorus and Its Compounds. — (a) Hold a small 
piece of phosphorus in tongs in the dark. What chemical reaction goes on? 
Why is phosphorus kept under water? How can phosphoric acid be made? 
Compare with experiment 8. 

(b) Test the solubility of sodium phosphate, Na 3 P0 4 , tricalcium phos- 
phate, Ca y (P0 4 ) 2 , and acid calcium phosphate, CaH 4 (P0 4 ) 2 . Which of the 
latter two would be chosen as the more quickly available fertilizer (p. 167) ? 

(c) Make a dilute solution of sodium phosphate slightly alkaline with 
ammonia, then add a few drops of a solution of calcium chloride. Treat some 
ground bones with dilute hydrochloric acid, and neutralize with ammonia. 
Compare the precipitate of calcium phosphate with that obtained in the 
first test. 

Ca 3 (P0 4 ) fi + 4HC1 = CaH 4 (P0 4 ) 2 + 2 CaCL 
calcium phos- 
phate in bone 

3CaH 4 (P0 4 ) a + 12NH 4 OH = Ca 3 (P0 4 ) 2 + 4 (NH^PO, + 12 H 2 

49. To Study Chlorine and Its Compounds. — (a) Put about one-half 
gram of manganese dioxide in the bottom of a test tube, and add a few drops 
of concentrated hydrochloric acid. Warm gently. The manganese dioxide 
furnishes oxygen for the following reaction: 

2HC1 + O = 2 CI + H 2 

Test the odor of the evolved gas by wafting a little of it towards the nose 
by a wave of the hand. Do not breathe the gas directly. Hang a damp 
strip of colored calico in the tube by means of a loosely fitting cork, and let - 
stand for 10 or 15 minutes. 

(b) Make a suspension of bleaching powder in water, and immerse in it 
a piece of the colored calico used in ( a ) . In two other test tubes put pieces 
of the calico into solutions of two other compounds of chlorine, such as 
NaCl, or CaCl 2 . Judged by these three tests and the one in ( a ) , what form 
of chlorine is evidently given off by the bleaching powder? Does the odor 
of the powder suggest the odor of the gas in (a) ? For what is bleaching 
powder used? For what is chlorine gas used? 

(c) Test the solubilities of the chlorides of Na, K, Ca, Mg, and Ba. 
10 



146 SOME COM X-METALS 

(d) To a dilute solution off a chloride add a fw drops of nitric add, 
then a few cjc. of silver nitrate solution. The precipitate is sifter chloride: 

XaCl + A&SQ = AgCl + HaNC 

Tkis is • nnircraaily-narrf feat for chloride*. 

Add a ffew ce. off concentrated sulfuric acid to 2 g. off sodium chloride 
in a test tube. Warm sect St. Compare the odor of the escaping gas to that 
off the vapors off a bottle off feydroehlorie acid. 

2 Nad + H^SO = 2 HC1 + Xa.SO* 

Hold moist blue litmus paper in the gas. Dip a glass rod into ammonia 
vmter. then hold the tod orer the nmuth of the test tube. Compare with the 
test made in experiment 43 (ej 



n. To Prepare a Table of Solubilities.— fal By means of the results 
off the previous experiments, fill in as many of the spaces in the table as is 
Iff certain salts, as silver carbonate and magnesium nitrate, have 
worked with, leave the spaces blank. Use the following abbrevia- 
te express the solubility: 



- . -".;.- - :.;' It- 



State briefly how you would test an unknown substance to see 
whether it is a carbonate, chloride, sulfate or phosphate. 





Tabu: X 


~. 


: . - .. ;-.-.. - ... ■ - .,.-,« 


N , 


:: 




- 




Cu 


- 



Bn 



CHAPTER XI 

THE AGRICULTURAL CHEMICAL ELEMENTS 

In the preceding chapters, as we discussed each chemi- 
cal element that came to our notice, we mentioned two 
general kinds of uses for that element or its compounds. 
One was its uses in the plant or in the animal body, the 
other was its uses outside of the body. The latter uses 
determine whether it occurs in our manufactured articles, 
our clothing, fuels, building materials, cleaning agents, 
medicines. In this connection we discussed some twenty- 
five different elements, and found that some of them are 
always found in plants, some are always found in animals, 
some are occasionally found in both of them, and some are 
never found in either. In this chapter we wish to get a 
general view of the elements which go to make up the 
bodies of plants and animals, as these form the basis 
of agriculture. 

The Occurrence of These Elements. — It might be well at 
the outset to point out that of all the fifteen or so elements 
found in animals and plants, none are found there as 
elements, but only as compounds. Hence, when we speak 
of sulfur occurring in this or that part of the animal 
body, we do not mean uncombined sulfur, but a com- 
pound of sulfur. Oxygen is the only free element that can 
be utilized by the higher plants and animals, and this is 
soon combined with substances in the body in the proc- 
ess of combustion. Some argue that free nitrogen is 
utilized by the legumes ; but this is not the case, since it is 
the bacteria on the roots of the clover, and not the clover 
plant itself, that absorbs the free nitrogen. And in this 

147 



1 is THE AGRICULTURAL CHEMICAL ELEMENTS 

connection it should be stated that when we say animals 
and plants, we mean the higher animals and plants, and 
usually those of agricultural importance. The bacteria, 
fungi, and lower forms of animal life have many pecu- 
liarities in their nutrition and ways of living that would 
prove exceptions to the above statements. 

The following classification of the chemical elements 
connected with agriculture will aid in getting the proper 
viewpoint concerning them: 

1. The eh ments necessary to plant life: 

Carbon, hydrogen, oxygen, nitrogen, sulfur, phos- 
phorus, iron, potassium, calcium, magnesium. 

2. The elements not necessary to plants, but usually 

found in them: 
Chlorine, silicon, sodium, aluminum, iodine. 

3. The elements necessary to animal life: 

The same as group 1, besides chlorine, sodium, 
and iodine. 

4. The elements found in the soil: 

All the elements mentioned in the first three 
groups, besides several others of slight 
importance. 

Elements in the Soil. — The soil contains all the elements 
that are found in either plants or animals. This is to be 
expected, since the animal gets its elements by eating 
the plants, and the plants get theirs from the soil. It 
musl not be forgotten that plants get practically all of 
their carbon from the air, although a small amount is 
found in soils from the decay of plant material there. 
Soil- \<ry often contain other elements besides the fifteen 
enumerated above, when the rocks from which the soil 
originated contain them. Thns, copper, arsenic, barium, 
zinc, and manganese are frequently found in soils in 
Bmall quantities. 

Absorption by Roots. — When a plant is growing in soil, 



THE ELEMENTS NECESSARY FOR PLANTS 149 

the soil water dissolves the compounds of the soil, and the 
plant absorbs this solution through its roots. To a certain 
degree, the root can select the materials which it wants 
from this solution, and reject the ones it does not want. 
This is so only to a limited extent, however. For example, 
if copper sulfate is added to a soil, the plants growing 
there cannot always reject it altogether from the soil 
solution. They will up to a certain extent ; and they will 
tolerate a certain amount of it in their tissues without 
being harmed ; but if the amount of copper sulfate in the 
soil is so great that these limits are passed, the plant will 
be harmed by it and perhaps killed. In the same way, if 
a beneficial compound as potassium nitrate is found in 
excess in a soil, as it sometimes is in certain semi-arid 
regions, the plant cannot absorb just the amount it needs, 
but will be literally forced to overfeed, and thus be 
harmed. Certain plants have become accustomed to grow- 
ing in salt water; these plants have not learned how to 
reject the unwanted amounts of salt, but their tissues 
have learned how to thrive in spite of the excess. 

The Elements Necessary for Plants. — In the second group 
in the above outline, there are a number of elements which 
are "not necessary to plants, but usually found in them." 
This naturally suggests two questions : Why are these 
elements found in plants if they are not necessary? and, 
how do we know that they are not necessary? The first 
question has already been answered: The plant roots 
absorb the soil water and all substances that are dissolved 
therein, whether the plant needs them or not. If the un- 
necessary elements were a part of the rocks and minerals 
from which the soil originated, they are naturally in the 
soil, and are then found also in the plants growing in 
that soil. 

But how do we know that the plant does not need 
them? This has been reached by a long series of careful 



150 THE AGRICULTURAL CHEMICAL ELEMENTS 

experiments, in which many varieties of plants have been 
grown in artificial soils. The soils consisted of pure, care- 
fully-washed Band, which is silicon dioxide, Si0 2 , to which 
is added solutions of the salts of all the elements but one 
found in natural soil. That is, to one pot of sand is added 
all the fifteen elements above, but with sulfur omitted; 
in another, calcium is omitted; and so on. By this method, 
after many different trials by many workers, we now know 
what elements various plants absolutely have to have in 
order to grow and produce seed. From these experiments 
we are able 4 to state in the above outline which elements 
are necessary, and which are not, in the life of the plant. 

The Elements Necessary for Animals. — When it comes to 
deciding which elements are necessary in the life of the 
animal, we have a very different problem. We cannot feed 
the animal a series of salt mixtures with one element 
omitted, and expect the animal to grow. The food of 
the animal is plant material, or prepared products from 
plant materials. When a cow eats a shock of corn, she 
eats all the chemical elements that the corn obtained from 
the Boil. In older to eliminate certain elements, we would 
have to take that shock of corn and prepare from it pure 
substances, as pure cornstarch and corn oil, which con- 
tain only C, H, and 0, and pure corn protein, which 
contains only 0, H, 0, N, and S, and feed these to the cow, 
\\\cv with Baits of the various other elements which 
we wanted to feed. It can be readily seen that this would 
})(• a next to impossible task. 

Such experiments have been conducted on small ani- 
mals like rata and rabbits, but most of our information 
along these lines is reached in another way. This is by 
the direct analysis of the tissues of animals. If a certain 
element is always formed in certain tissues, and if an- 
other element is never found in any tissue, it is pretty 
good evidence thai the one element is necessary, and that 



ORIGIN OF LIVING MATTER 151 

the other is unnecessary, to the well-being of the animal. 
We could not use this method in the case of plants, for they 
absorb everything that is in the soil, irrespective of any 
use they may have for it. Animals, however, have a much 
greater selective ability; when an element is taken into 
their body and it is not wanted, it is promptly eliminated, 
either through the intestines or the kidneys. Thus, if an 
animal day after day eats plant material which contains 
silicon, and if no silicon is found in any of its tissues, 
and if the silicon in the urine and faeces amounts to the 
same as that eaten in the food, the presumption is that that 
animal does not need the element silicon. From this kind 
of study we have been able to determine the list of ele- 
ments necessary for animal life. It will be noticed that the 
animal requires three elements that the plant does not; 
it is very fortunate that nature has seen fit to have plants 
take up these elements from the soil, even though they 
be not for the plants ' own use. 

The Agricultural Chemical Elements. — In summary of 
what has been said concerning these agricultural chemical 
elements, we can bear in mind that there are about fifteen 
of these elements ; that the soil furnishes the plants with 
all of them but carbon, which is obtained from the air; 
that these elements must exist in the soil as compounds 
soluble in water; that if any one of the ten elements essen- 
tial to plant life is lacking, the soil will not support plant 
growth; that animals obtain all their chemical elements 
from the plants which they eat, and that if the plants 
contain elements not wanted by the animal, the latter 
excretes them from its body. 

Origin of Living Matter. — It is interesting to note again 
at this place that water is the most abundant of all com- 
pounds in living organisms. Over three-fourths of the 
weight of all animals is water, and many plants are nine- 
tenths water. Also, it should be pointed out that the 



THi: AGRICULTURAL CHEMICAL ELEMENTS 

ihemical elements mentioned above are found in 
water. There mnsl obvionsly be ><»iik j connection 
between these facts. Mathews, in his "Physiological 
mistry, " - s: "'' is certainly not without signifi- 
cance that living matter is so watery and contains the 
- ts r the sea. Et wonld appear probable from this that 
living matter originated either in the sea itself or, per- 
pool of water which contained the com- 
mon salts. " 

QUESTIONS 

1. W Hum an<l Bilioon found in plants, when the latter have no 

for them ! 

2. W s get all the chemical elements necessary to build up 

Uteii 

.ime the elements necessary for animal life. 
4. What happens if one necessary element is lacking in a plant's or an 

animal's f 
.'.. What is the only uncombined element used by animals in their living 

pro eases Vhat do they use it fori 
♦;. Bow wonld yon prove whether chlorine is a necessary element for the 

corn plant 1 

tists 1 • lieve that life originated in the sea"? 

LABORATORY EXPERIMENTS 

51. To Show the Presence of Carbon in Plant Tissues. — Place some 
eornmeal, chopped hay. or other plant material in a porcelain dish and heat 
with the burner. The charring indicates carbon. What other substances 
ha\« ntain carbon 1 (See experiment 22. 

52. To Show the Presence of Some Mineral Elements in Plant 
Tissues. — (a Ignite some chopped hay in a porcelain dish to a white ash. 

two burnt rs asary. When cool, add water to the ash. 

1 little o! it. and test the filtrate for chlorides. (See experiment ■ 

I dilute hydrochloric acid to the remainder of the 
a«h in order to dissolve more o! it. filter and test separate portions of the 
r phosphates and sulfates test 1 annates, make 1 

ith ammonia, then slightly a<id with nitric acid. Heat to 
<•.<•. of ammonium m tlybdate solution.* 
T<-~t for caleium by making one portion sli ghtly ammoniar-al and 

immonium molybdate solution i> made as follows: Dissolve 50 g. 

concentrated ammonium 

slowly and with constant stir- 

lution into a mixture of 244 cc of concentrated nitric acid 

of water. Keep the mixture in a warm 

■.•fully pour off the dear liquid from any sediment 

and keep ii ppered 1- 



LABORATORY EXPERIMENTS 



153 



then adding a few c.c. of potassium or ammonium oxalate solution, 
precipitate is calcium oxalate: 

+ 2KC1 



K*C 2 4 + 


CaCl 2 


= CaC.,0 4 


potassium 




calcium 


oxalate 




oxalate 



The 



(d) If a portion of the ash will not go into solution it indicates silica. 

(e) Name all the chemical elements that have been proved present in 
plant material, including the two in experiment 9. What other elements 
are probably present (Chapter XI) ? These elements cannot easily be de- 
tected by tests, hence the tests have not been included in these experiments. 

53. To Show What Mineral Elements Are Needed by Growing 
Plants. — Wash 4 or 5 pounds of the cleanest sand obtainable by stirring 
it in a pail of water, letting it settle,, then pouring off the water. Repeat 
three times, then dry the sand. 

Make up the following solutions : 



I 




11 




Ill 




Water 


1000 c.c. 


Water 


1000 c.c. 


Water 


1000 c.c. 


KNO3 


1.0 g. 


NaN0 3 


1.0 g. 


KNO3 


1.0 g. 


NaCl 


1.0 g. 


NaCl 


1.0 g. 


KC1 


1.0 g. 


MgS0 4 


0.5 g. 


MgS0 4 


0.5 g. 


MgS0 4 


0.5 g. 


CaH 4 (P0 4 )2 


2.0 g. 


CaH 4 (P0 4 ) 2 


2.0 g. 


CaH 4 (P0 4 ) 2 


2.0 g. 


FeS0 4 


0.3 g. 


FeS0 4 


0.3 g. 


FeS0 4 


0.3 g. 


IV 




V 




VI 




Water 


1000 c.c. 


Water 


1000 c.c. 


Water 


1000 c.c. 


KNO3 


1.0 g. 


KNO3 


1.0 g. 


KNO3 


1.0 g. 


NaCl 


1.0 g. 


NaCl 


1.0 g. 


NaCl 


1.0 g. 


Na 2 S0 4 


1.0 g. 


MgS0 4 


0.5 g. 


MgS0 4 


0.5 g. 


CaH 4 (P0 4 ) 2 


2.0 g. 


Na 2 HP0 4 


2.0 g. 


CaH 4 (P0 4 ) 2 


2.0 g. 


FeS0 4 


0.3 g. 


FeS0 4 


0.3 g. 






VII 




VIII 




IX 




Water 


1000 c.c. 


Water 


1000 c.c. 


Water 


1000 c.c. 


K 2 S0 4 


1.0 g. 


K 2 S0 4 


1.0 g. 


KNO3 


1.0 g. 


NaCl 


1.0 g. 


NaN0 3 


1.0 g. 


NaN0 3 


1.0 g. 


MgS0 4 


0.5 g. 


MgS0 4 


0.5 g. 


MgCl 2 


0.5 g. 


CaH 4 (P0 4 ) 2 


2.0 g. 


CaH 4 (P0 4 ) 2 


2.0 g. 


CaH 4 (P0 4 ) 2 


2.0 g. 


FeS0 4 


0.3 g. 


FeS0 4 


0.3 g. 


FeCl 3 


0.3 g. 


X 

Water 


1000 c.c. 










KNO3 


1.0 g. 










NaCl 


1.0 g. 










MgS0 4 


0.5 g. 










CaCl 2 


2.0 g. 










FeS0 4 


0.3 g. 











Place about 2 inches of the sand in the bottom of 10 pint Mason jars. Label 
these jars as follows: I, complete; II, no K. ; III, no Na; IV, no Mg; V, no 
Ca; VI. no Fe; VII, no N0 3 ; VIII, no CI; IX, no S0 4 ; X, no P0 4 . The 



IS I THE ACK [CULTURAL CHEMICAL ELEMENTS 

making ol the solutions and the preparation of the jars may be divided up 
among the Btudents. Place 10 timothy, wheat, barley or rye seeds in the 
Band in each pot, moisten the sand with the appropriate nutrient solution, 
and watch the developmenl of the plants. Keep the jars covered with glass 
until the leaves appear, then leave them uncovered for the sake of aeration. 
Keep the -and damp, but not soaked completely with water. Every seventh 
day water with the nutrient solution and the other days with distilled water. 
It" the nutrient solution is used up before the completion of the experiment, 
do not make up more solution, hut used distilled water, since the above 
quantities of salts are sufficient for this number of plants. Higher amounts 
injure them, 

Make careful observations on the development of the plants, noting 
particularly their height, color, and general thriftiness. Keep a record of 
all observations, noting which pots show the best growth. 

Why was the -and washed? Why is distilled water used? What ele- 
ment- are apparently necessary for plant growth? The lack of what element 
causes the yellowing of the leaves? 



CHAPTER XII 

THE SOIL 

Origin of the Earth. — Astronomers tell us that in the 
beginning the earth was a white-hot mass of gas and 
liquid, more or less like the sun is at present. It prob- 
ably consisted of the same eighty chemical elements that 
now constitute the earth; but the temperature was so ex- 
ceedingly high that none of the elements were combined ; 
they existed as free elements. But the mass gradually 
cooled; and as the temperature became lower, some of 
the elements could combine. Thus, silicon and oxygen 
combined to form quartz, hydrogen and oxygen combined 
to form water, carbon and oxygen to form carbon dioxide. 
One after another, simple compounds were formed. Then 
some of these compounds combined to form other com- 
pounds, including minerals. During these changes the 
heavier elements and compounds gradually worked to- 
wards the centre of the ball of gas, and the lighter ones 
towards the outside. As the cooling process continued, 
more and more minerals and other compounds were 
formed; finally the greater proportion of the gas had 
cooled to a liquid state ; and as it cooled still further, the 
molecules of one mineral would tend to collect together 
and crystallize into a solid, just as salt or sugar will 
crystallize from their concentrated solutions. Finally, 
the whole outer shell of the fluid ball became a solid crust, 
consisting of a large number of minerals in lumps 
cemented together. To be sure, some of these masses 
of minerals were as big as mountains, but they were small 
in comparison to the whole earth. One element, nitrogen, 
did not combine to any extent with other elements, and 

155 



THE SOIL 

remained on the outside of the ball as the atmosphere. 
Another element, oxygen, was so abundant that although 
it had combined to form nearly half of the weight of the 
-olid ball, there was still a great deal left over, which 
Btayed in the atmosphere with the nitrogen. The crust 
of the earth, although solid, was still very hot; hence the 
oxygen and the hydrogen that had combined to form 
water could not remain on the earth as liquid water, but 
existed in the air as water vapor. Probably all the carbon 
in the world was in the form of carbon dioxide, and prac- 
tically all of this was in the air, as the lime in the earth's 
crust was still too hot to retain the carbon dioxide as cal- 
cium carbonate. (See the chemistry of limestone, p. 100.) 
Thus the earth's atmosphere at that time was consider- 
ably deeper than it now is, and besides the present 
amounts of nitrogen and oxygen, there was an immense 
quantity of water vapor and carbon dioxide. 

Beginning of Life and of Soil.— When the earth had 
cooled sufficiently to allow water to condense on it, the 
wear-ai id-tear process of erosion commenced. The water 
falling in torrential rains flowed from the higher spots to 
the lower, dissolving some of the minerals, exerting chemi- 
eal action on others, and exposing new layers of them to 
the atmosphere. It carried the material to the lower and 
hotter portions of the crust, and then, evaporating, left 
the mineral residue behind. In this way the primitive 
were formed, and the highlands or mountains were 
worn down. The waters of these seas thus contained 
all of the chemical elements that had existed in the min- 
erals which the water could dissolve from the mountains 
and The minerals which the water could dissolve 

and carry to tie' sea contained the fifteen elements dis- 
•d in the lasl chapter; that is. those necessary for 
life. Bence the supposition that living organisms had 
their origin in tin- sea. 



THE SOIL-FORMING MINERALS 157 

The earth continued to cool; water and air continued 
to exert their action on the rocks and minerals; these 
were broken into smaller and smaller pieces by colliding 
against each other in streams ; and still other processes of 
disintegration continued, over long periods of time. 
Finally, parts of the earth's surface were covered with 
fine rock debris. This was the beginning of soil. It was 
not soil as we ordinarily think of it until there were 
plants growing in it. This probably took place when the 
heat and moisture conditions were so favorable that some 
of the organisms living in the seas could gradually accus- 
tom themselves to living in the soil. When they did so, 
there was not only life in the sea, but life in the soil on 
land as well. More and more of the earth was covered 
with soil, more complicated forms of plant and animal life 
began to appear, the earth became sufficiently cool so that 
more and more of its surface would support life, the moun- 
tains became smaller and the seas larger, there was less 
water vapor in the atmosphere, a great deal of carbon 
dioxide was absorbed by plants, stored up in their bodies, 
and then the carbon converted into coal by the decay of 
the plants. Thus the world as we now know it was evolved. 
The process took an inconceivably long time, and of course 
was far more complicated than we have outlined. Fur- 
thermore, changes are still taking place; the earth will 
continue to cool off, the frigid zones will move farther 
and farther towards the equator, and finally the crust of 
the earth will become too cold to support life. 

The Soil-forming Minerals. — Since our present soil had 
its origin mainly in the minerals of the earth's crust, it 
is important that we know something of the nature of 
these minerals, since each mineral furnishes a particular 
group of elements to the soil. 

As we have seen above, the original rock of the earth's 
crust is a mixture of many minerals. A mineral is a 



1 ;>s THE SOIL 

definite chemical compound, and each mineral always has 
\mposition. Granite, for instance, is not a 
mineral, for it varies in composition; it is a mixture of 
minerals, which can be seen in individual crystals if the 
freshly-broken Burface is carefully examined, especially 
with a Lens. A few of the more important minerals are 
described below: 

Quartz, SiOo, we have mentioned before as being the 
most abundanl compound in the earth. All sands and 
sandstones are composed of it; the modified sandstone 
called quartzite is practically all silicon dioxide. Chirt, 
flint, agate, opal, and amethyst are forms of this mineral. 
It contributes no plant -food elements to the soil. 

Feldspars form a group of very important minerals. 
Next to quartz, they are the most abundant of all minerals. 
All feldspars contain aluminum and silicon, and at least 
one other metal, which metal determines the kind of feld- 
spar a particular one is. Thus, sodium, potassium and 
calcium feldspar are common, the most important being 
the potassium. The pink and green particles in granite 
are feldspars. 

Micas are soft minerals, characterized by their tend- 
ency to split into thin, transparent sheets: The "isin- 
Lrhiss" of coal stoves is mica. It is very abundant in 
granite rocks, constituting the shining flakes in them. 
They are compounds of aluminum, silicon, oxygen, 
and potassium, although some of them contain iron 
and calcium. 

Apatite is essentially a phosphate and a chloride of 
calcium combined, and is practically the only phosphorus- 
bearing mineral in our rocks and soils. 

Kaolin is an aluminum silicate with no other metal in 
it- composition. It is the basis of all clays. With water 
it forms ;i sticky, adherent mass, which when baked be- 
comes very hard and brittle. This property is valuable 



METHODS OF SOIL FORMATION 159 

in the making of bricks and pottery, as we have seen ; but 
it is otherwise in soils, as clayey soils are noted for their 
stickiness in wet weather, and their hardness in dry, hot 
weather. Since kaolin results from the decomposition of 
micas, feldspars, and other granite minerals, clay soils are 
usually rich in plant-food elements. 

Calcium carbonate and magnesium carbonate and their 
importance in the earth have already been discussed. 
Although very abundant in rocks, and sometimes forming 
deep beds and constituting whole mountains, they are 
only moderately abundant in most soils, since they readily 
leach out in water containing carbon dioxide, and in this 
way give rise to most of the hardness of water. River and 
sea waters contain a great deal of calcium and magne- 
sium bicarbonates. 

Selenite is calcium sulfate, called also gypsum and 
"land plaster." It is the principal source of the sulfur of 
plants. It is more soluble in water than most other min- 
erals, hence is found abundantly in drainage waters. 

Iron pyrites and limonite are two common iron-bearing 
minerals in rocks. The former furnishes the yellow and 
green colors to most sand and clay beds. These minerals 
are the source of iron to plants. 

Talc is a magnesium silicate. It is commonly known 
in mass as soapstone, although in small granules it is a 
constituent of many rocks. 

There are a great many more minerals found in all 
soils, but the above are the most abundant. They are also 
the most important, since they furnish all the elements 
needed by plants and by animals with the exception of 
iodine, which occurs in only minute traces in some little- 
known minerals. 

Methods of Soil Formation. — Thus, we see briefly that 
the soil was formed by the disintegration of the minerals 
of the earth. To this decayed rock material was added de- 



L60 THE SOIL 

caved plant material as soon as plants became abundant 
in the primitive soil. Our soils to-day contain a consider- 
able and very important amount of decayed plant remains, 
called humus. The actual processes of soil formation 
involved several factors, the chief of which we shall 
now discuss. 

Water is probably the most important agent in soil 
formation. Rain seeps into the crevices of rocks, dissolves 
ont the most soluble minerals and leaves the less soluble 
behind. It even acts chemically on some minerals. When 
it contains carbon dioxide in solution it is -very active 
chemically. We have already seen how limestone is dis- 
solved by carbonated water: 

CaCO» + H 2 = C0 2 + Ca(HC0 3 ) 2 

The calcium carbonate is very insoluble, the calcium bicar- 
bonate very soluble. Many other minerals are acted upon 
similarly; as apatite, gypsum, feldspar, mica, and 
even quartz. 

Running water wears away rocks by grinding one on 
another. It also carries away the finer particles and ex- 
poses new surfaces of rocks to the wearing action. 

The freezing and thawing of water are powerful forces 
in splitting rocks. The water gets into crevices, and as 
it freezes it expands with great force and splits the rock. 
When the water thaws it flows into the crack a little 
farther, and on freezing continues the process. It is 
recognized by farmers that spring and fall weather of 
many alternate freezings and thawings is very beneficial 
to soils. 

Frozen water in the form of glaciers has been the main 
agenl in the formation of soils in most of our Northern 
States. In one of the later geological periods huge gla- 
ciers formed in Canada and slowly moved southward (Fig. 
42). These masses of ice were hundreds of miles in extent, 



METHODS OF SOIL FORMATION 



161 



and hundreds of feet in depth; they ground off whole 
hills, pulverized rocks, and dug deep gashes in the earth 




Fig. 42. — Map of North America, showing the areas covered by the three great ice sheets 

of the Glacial Period. A, Labrador; B, Keewatin; and C, Cordilleran ice sheet. The masses 

of ice carried along enormous quantities of rock and soil, which were deposited when the 

ice melted. This material constitutes the present soil in the glaciated regions. 

like the basins of the Great Lakes. And when they melted, 
they deposited their loads of rocks, gravel, and sand in 
piles. These gravel piles contribute most of the present 
11 



162 THE SOIL 

hills in the glaciated areas of the Northern States and 
Canada. When the ice had melted and the climate became 
warmer, the surface of the earth in .these regions was 
covered with a new layer of rock debris, on which the other 
soil-forming agents set to w T ork and produced the wonder- 
fully fertile soils which are there at present. 

Winds hurl sand and particles against cliffs, and wear 
them off; blow the soil off of hills and expose new surfaces 
to the weather; and deposit fine silt particles over large 
areas to form the loess soils of our Western States. 

The roots of trees, pushing their Way into rock crevices 
and wedging them apart by the force of their growth, 
exert a great effect in the breaking up of rock into soil. 

Animals, such as earthworms, ants, gophers, and moles, 
are important agents in moving soil about, aerating it, 
bringing subsoil to the surface, and aiding in the decay 
of plant remains. 

Kinds of Soil. — It will be readily understood now how 
soils from various parts of the earth can vary so widely in 
composition, character, and fertility, depending first, upon 
the composition of the underlying bed rock, or, in the case 
of glacier, water, or wind-carried soils, upon the minerals 
of the region from which they came ; and second, upon the 
methods of soil formation themselves. A soil might be 
low in phosphorus if there was little apatite in the rocks. 
A soil of granite origin is likely to be clayey, due to the 
decomposition of aluminum-bearing minerals. A soil 
deposited by wind will consist entirely of fine particles. 
A soil deposited from water, as the soils from old lake 
and river bottoms, is likely to be sandy. Soil in a 
ulaciateel region is likely to occur in patches of varied 
character and to be full of stones, both large and small. 
A soil in a limestone region may or may not be rich in lime, 
depending upon how extensive has been the leaching of 
carbonated water through it. 



KINDS OF SOIL 163 

Soils are classified in many ways. Since the method of 
classification depends mainly upon the viewpoint, no arbi- 
trary classification will be given here, but the discussion 
of soils will be given from various viewpoints. Thus, on 
the basis of position, we speak of soils and subsoils; from 
the standpoint of the rainfall of the region we have arid 
and humid soils; because of mechanical differences we 
have sand, clay, loam, much, and peat soils; depending 
upon the origin and the method of formation we have 
glacier, loess, sedentary, transported, limestone, granite, 
and lava soils. 

The most conspicuous difference between soil and sub- 
soil is the color ; this is due to the decayed plant matter or 
humus in the soil. There is usually less calcium carbonate, 
potassium, and iron compounds in the soil, as these are 
leached away and used by plants to a considerable extent. 
The subsoil is more fine grained and compact, as the finer 
particles of the soil are washed down into it. For this 
reason the subsoil is heavy and is not easily aerated, and 
hence is much less fertile than the soil. 

Arid soils are not subjected to the leaching action of 
water to the extent that humid soils, are ; hence the amount 
of available plant food is usually greater in the arid soils. 
They were formed not so much by the action of air and 
water on the minerals as by the alternate freezing and 
thawing of water in the rock crevices. When arid soils 
are supplied with water, as by irrigation, they usually 
prove to be very fertile. 

By sand is usually meant the coarser particles of 
broken rock, consisting mainly of silicon dioxide, but also 
of many other minerals in smaller amounts. The term 
" sandy soil" means nothing definite. By it is usually 
meant a soil of rather coarse, loose, open texture, contain- 
ing little humus, holds water but poorly, and is rather 
infertile until organic matter has been added to it. Silt 



lt>4 THE SOIL 

consists of particles smaller than sand, and silt soils have 
a closer texture and hold water better than sandy soils. 
The loess soils of the Western plains consist mainly of 
silt deposited by winds. Clay is that portion of soil which 
consists of the very finest of particles ; the particles of clay 
are so fine that they do not settle when suspended in water. 
Since clay consists of finely ground-up mineral materials 
of all kinds, it contains an abundance of plant food. It 
holds water tenaciously, forming a sticky, adhering mass, 
thus making a soil that is worked with difficulty. The 
term loam is the most abused of all the words in soil ter- 
minology and usually means the least. Any soil which will 
grow crops, is somewhat dark in color, and is worked fairly 
readily is a loam ; and this is usually modified to ' ' sandy 
loam," "clay loam," and other terms. Peat is partially- 
decayed plant remains, as we saw in the chapter on coal. 
It occurs in marshes where certain characteristic grasses 
and mosses thrive. It contains very little mineral mate- 
rial, although what there is becomes readily available to 
plants when the peat marsh is drained and aerated. It 
absorbs water like a sponge; hence it is used to pack 
around the roots of nursery stock, and one variety is used 
in place of absorbent cotton in surgical dressings. When 
peat is so thoroughly decayed that plant stems and leaves 
can no longer be distinguished in it, and it has become 
very black in color and has been mixed with mineral soil 
to some extent, it is called muck. Muck is the typical soil 
of marshes. 

Soil types which derive their names from their method 
of origin have already been discussed sufficiently under 
tin- topics of the methods themselves, as loess, glaciated, 
and waU r-deposited or sedimentary soils. Our granite 
and lava -oils are usually very rich in plant-food elements, 
because the appropriate minerals are abundant in these 
rocks. ( lalcium carbonate is usually low, however, as it is 



THE MECHANICS OF SOIL 165 

leached out as rapidly as the soil is formed. We saw 
that limestone had its origin in the skeletons of sea-ani- 
mals; these skeletons carried with them parts of the 
softer portions of the animals as well, and thus limestone 
usually contains an appreciable amount of phosphorus, 
potassium, iron, magnesium, and other elements. When 
the limestone disintegrates in soil formation, the calcium 
carbonate is the most soluble of all the constituents ; hence 
the resultant limestone soil contains relatively little cal- 
cium carbonate and relatively much other minerals. Such 
soils are very fertile, although often they are benefited 
by applications of ground limestone. The majority of the 
soils of the Mississippi Valley are of limestone origin. 

The Mechanics of Soil. — The capacity of a soil to hold 
water and to absorb water, the rapidity with which it 
becomes warm in the spring, and the ease with which it 
can be plowed and hoed and kept in a pulverized con- 
dition, are spoken of as the mechanical properties of the 
soil. These depend almost entirely upon the proportion 
of sand, clay, and humus in the soil. Sand holds water 
very poorly ; therefore it is quickly drained in the spring, 
and it as quickly becomes too dry later in the summer to 
support plant growth. The particles do not adhere to any 
degree, hence sandy soils are always loose, easily worked 
and well aerated. Clay absorbs water very greedily; it 
also retains it just as greedily, and thus prevents plants 
from absorbing it. Thus a sandy soil containing 10 per 
cent of water will still keep plants from wilting, where a 
clayey soil with 15 per cent of water will not. If clay 
soils are worked when they are wet, they " puddle,' ' and 
form sticky lumps that, when dry, are hard, brick-like 
clods. This can be remedied by incorporating sufficient 
sand with the soil, or, more easily, by adding finely 
ground limestone, which "flocculates" the clay and re- 
duces the tendency to puddle. 



L66 THE SOIL 

Warm and Cold Soils. — The rapidity with which a soil 
becomes warmed by the sun is governed almost entirely by 
the amount of water in the soil. This is because water has 
a very high specific heat; that is, it requires more heat 
to raise the temperature of a pound of water one degree 
than that of any soil constituent. Therefore wet, poorly 
drained, clay and muck soils are always the last to become 
warm enough in the spring to promote plant growth. 
Drainage is the only cure for such soils. 

The humus of soils also largely governs the water- 
holding capacity, as it absorbs water even more readily 
than does clay. The following table shows this in 
actual figures: 





Pounds of water in 
1 cu. ft. of soil 


Soil high in sand 
Soil high in clay 
Soil high in humus 


28 
42 
51 



This explains why the addition of manure and other 
humus-forming material greatly benefits sandy soils. 
Since black materials always absorb more light and heat 
waves when exposed to the sun's rays than do materials 
that are not black, humus serves to produce warmer soils 
by absorbing more of the sun's rays. Humus is more 
important in soils chemically than mechanically, however, 
and it will be taken up from this standpoint later on. 

Chemical Composition of the Soil. — We have* seen what 
the origin of soils is; what minerals furnish the chemical 
elements necessary for plant growth; what effect the 
source of a soil and the method of its formation may have 
upon the amount of these elements in the soil. "We have 
yel to discuss the actual amounts of these elements pres- 
et) 1, and how the growth of crops and the chemical activi- 
in the soil may change these actual amounts. 

The accompanying table gives the approximate com- 
position of soils, both iii percentages and in the amounts 



TOTAL PLANT FOOD 



167 



of the various constituents in an acre six inches, assuming 
that the latter weighs 2,000,000 pounds. 





Table X 

Average Corn-position of Soil 






Percentage 


Amount in acre 
6 inches 


Silicon dioxide . . 


50-80 
8-14 
1-6 
0.5 -2.0 
0.5 -1.5 
0.1 -1.3 
1.0 -3.0 
0.02-0.2 
0.20-1.2 
0.03-0.15 
0.02-0.10 
0.02-4.0 


1,700,000 lbs. 


Aluminum 


200,000 lbs. 


Iron 


80,000 lbs. 


Calcium 


30,000 lbs. 




20,000 lbs. 


Sodium 


16,000 lbs. 


Potassium 


40,000 lbs. 


Sulfur 


2.000 lbs. 


Chlorine . 


16^000 lbs. 


Phosphorus 


1,600 lbs. 


Nitrogen 


1,000 lbs. 


Humus 


40,000 lbs. 







Total Plant Food. — It will be seen that although the 
percentage of some of the plant-food elements is small, 
the total amount in an acre is very large. Also, it is 
apparent that sulfur, phosphorus, and nitrogen are the 
least plentiful of these elements. When the above figures 
are compared to those in the table (p. 182) which gives the 
amounts of the various elements contained in an acre of 
various crops, it will be seen that even the scarcest ele- 
ments in the soil are still sufficient to supply crops for 
a great many years. Thus, a thirty-bushel crop of wheat 
contains about nine pounds of phosphorus ; 1600 pounds 
of this element in an acre six inches of soil would then 
support about 175 such crops. Similarly, there is enough 
of the other scarcer elements to support ordinary crops 
for several hundred years. We know, however, that con- 
tinuously cropped soils become unproductive long before 
that time. In other words, soils become infertile while 
there is still an abundance of plant-food elements in them. 



168 THE SOIL 

The reason for this lies in two facts which we have 
already considered. The first is, that plants require all 
their food in solution. The second is, that the decomposi- 
tion of soil and rock minerals into water-soluble forms is 
a Blow, gradual proees>. 

Available Plant Food. — Xow, the analyses of soils in the 
table on page 167 give the total amount of those ele- 
ments in the soil, irrespective of whether they are in a 
soluble or insoluble form. Since the greater proportion 
of each of them is still in the insoluble mineral form, such 
analyses really give us very little idea of the fertility of 
a soil. Thus in soil studies we have to deal with two 
classes of soil constituents, those that are available to 
plants, and those that are unavailable. 

It is often found that the total phosphorus or potas- 
sium in a soil is very large, sufficient for years of bumper 
crops, and yet that soil will not produce those crops. The 
application of fifty pounds of readily-available phos- 
phorus or potassium fertilizer, however, works wonders 
in increasing the fertility. 

Chemical Analysis of Soils. — It might seem that all the 
chemist would have to do would be to dissolve out with 
water the water-soluble material and this would be the 
portion available to plants. Unfortunately, however, soil 
behave- ><> differently towards water in this form from 
what it does towards the soil water and the roots of plants, 
that such a water extract gives very little information as 
to the fertility of the soil, or as to the fertilizer require- 
ments. In fact, one thing that agricultural chemistry has 
failed to give us so J<ir is a method by which ice can judge 
by chi mical analysis the value of a soil. To be sure, an 
analysis might suggest that more humus might be bene- 
iicial, or that lime is needed to correct acidity, or that 
some one elemenl i> suspiciously low; but it could not 
give ofl grounds for prophesying what crop would grow 



LABORATORY EXPERIMENTS 169 

best, or what fertilizing element would be most effective. 
Factors in Soil Fertility. — In soil fertility, then, we have 
to deal with a number of factors. The soil must absorb 
large quantities of water, and yet it must not become 
water-logged and soggy, and it must give up the water 
readily to plants. It must not only contain sufficient avail- 
able plant food for all crop requirements at the time 
being, but it must also contain an abundant supply of 
unavailable food, which can be constantly and steadily 
reduced to an available form as fast as needed. It is this 
last process of rendering the insoluble minerals into avail- 
able form, that the farmer has under his control to a 
considerable extent. The chemical changes that take place 
in the soil and the methods of controlling them will be 
discussed in the next chapter. 

QUESTIONS 

1. What has been the most important agent in the wearing down of moun- 

tains and in the formation of soil? In what different ways does 
it act ? 

2. Where did life probably originate? 

3. When could plants begin to live in soil? 

4. Make a list of the most important soil minerals, indicating what chem- 

ical elements necessary for plant growth are found in each. 

5. State the various soil-forming agents in the order of their importance. 

6. How can soils be classified? 

7. What is sand? Silt? Humus? Subsoil? Limestone? Peat? Loam? 

8. Explain how the moisture-holding capacity of a soil depends upon the 

amount of sand, clay, and humus in it. 

9. What is meant by total plant food and by available plant food in soils? 

10. What does a chemical analysis of a soil indicate? 

11. What are the most important scarce elements in soils? 

LABORATORY EXPERIMENTS 

54. To Show the Presence of Various Mineral Elements in Soil. — 
(a) Leach about 100 g. of sandy loam with hot water acidified with nitric 
acid, filter through double filter paper until the filtrate is as clear as pos- 
sible, then test for chlorides. 

(b) Boil 50 g. of soil with 100 c.c. of 20 per cent hydrochloric acid for 
10 or 15 minutes, cool, filter, wash the soil on the filter somewhat, then use 
the filtrate for testing as follows: 

(c) Add a few drops BaCl^ solution to a few c.c. of it. This tests for 
what? 



170 THE SOIL 

(di Make 10 c.c of it faintly ammoniacal. What is the precipitate? 
Add a few drops of a solution ot potassium oxalate. The granular precipitate 
ia calcium oxalate. 

(et If the solution is yellow, iron is present, since FeCl 3 is yellow 
in solution. 

(f) Make 10 c.C. of the solution alkaline with ammonia, then slightly 
acid with nitric acid ; warm to ()f>° C. and add a few c.c. of ammonium molyb- 
date solution. What does this test indicate? Why couldn't the extract of 
soil in (b ) be used for testing for chlorides? A great many other elements are 
found in soil, but their tests are not sufficiently simple to be given here. 

55. To Study the Humus in Soil. — Shake about 100 g. of black soil for 
one minute in a 200 c.c. cylinder containing 1 per cent hydrochloric acid. 
Let the soil settle, then pour off the acid. Repeat, then repeat twice with 
water. Then add 100 c.c. of 4 per cent ammonia and shake. The brown- 
ish or blackish colored material that dissolves is the humus combined with 
ammonia. Acidify some of the humus extract with hydrochloric acid. Ex- 
plain the result. Evaporate the rest of the solution to dryness in an evap- 
orating dish. Hold a flame under the dish. The charring proves that 
humus contains what? 

56. To Compare the Water-holding Capacity of Different Kinds of 
Soil. — Obtain some dry sand, loam, clay, and peat. Weigh out 20 g. of each 
in shallow dishes, then pour water from a graduated cylinder on to them 
until they are thoroughly saturated with water, and the water is just be- 
ginning to run away from the substances. Record the c.c. of water absorbed 
by the same amounts of these materials. How can the moisture-holding 
capacity of a soil be improved? 

57. To Show the Effect of a Mulch Upon the Evaporation of Water 
From a Soil. — Fill two tin or glass containers of the same size to the 
depth of two inches' with loam soil. Pack the soil down somewhat firmly, 
then wet thoroughly. Stir the surface of the soil in one dish until it is thor- 
oughly tilled. Then weigh each dish, and set aside in a warm place. Weigh 
each day thereafter, noting any effect that the mulching may have on the 
rate of water loss. What is the fundamental principle of dry farming? 

58. To Show the Effect of Color on the Temperature of Soil. — Fill 
two boxes about one foot square with soil. Cover the surface of one with 
ground charcoal, bone-black, or some other black powder, and the other with 
ground gypsum, chalk, or other white powder. Insert the bulb of a 
thermometer in the soil in each box and expose the boxes side by side to the 
direct rays of the sun. Record the temperature in each box every 15 
minutes for two hours. 



CHAPTER XIII 

CHEMICAL CHANGES IN THE SOIL 

From the previous discussions we have seen that the 
soil is not a fixed material, with unchanging composition, 
but that it is the seat of ceaseless activities and changes. 
Kocks and minerals are constantly being decomposed into 
soil particles ; some of the soluble material from these is 
being washed away; plant remains are decaying in the 
soil and forming new compounds ; rain brings down for- 
eign substances from the atmosphere ; manure and fertil- 
izers are being added. What chemical changes do these 
things actually bring about? Which changes are good 
and which are bad, and how can they be controlled'? 

Decomposition of Minerals. — As we learned in the last 
chapter, only a small proportion of the total mineral 
nutrients of a soil is available at any one time for crop 
use. It is very necessary, then, that fresh supplies of 
these nutrients be made available continuously. One of 
the most active agents in decomposing minerals is water 
containing dissolved carbon dioxide. We have seen how 
this affects limestone (p. 102,). The familiar fertilizer, 
rock phosphate, is practically insoluble in water; in the 
presence of carbon dioxide, however, it is converted into a 
soluble phosphate. Feldspars and micas have their potas- 
sium set free under the influence of carbonated water. 
It is therefore important that soil water contain plenty 
of carbon dioxide; and this is furnished by the humus. 

Formation of Humus. — Humus is the decayed or decay- 
ing organic matter of the soil; it consists of the remains of 
plant and animal bodies which are being used as food by 
bacteria, fungi, and molds, and by them being broken 

171 



172 CHEMICAL CHANGES IX THE SOIL 

down into a complex mixture of substances which have 
a black color. Usually, the blacker the soil the more 
humus it contains. 

Mechanical Effects cf Humus. — Humus is a gummy, 
sticky material. Since it thus serves to cement soil par- 
ticles together, the addition of humus to sandy soils 
makes them more compact. As we have mentioned before, 
humus absorbs water very greedily. It therefore aids the 
water-holding capacity of sandy soils. On clayey soils, 
however, it apparently has an opposite effect; and the 
addition of manure and other humus-forming materials to 
clays is Avell known to be very effective in "loosening up" 
their texture and making them more tillable. 

Chemical Properties of Humus. — The above functions of 
humus are physical or mechanical. Its chemical proper- 
ties are probably far more important even than these, for 
the following reasons: (1) The humus contains all of the 
nitrogen of the soil; (2) it furnishes all the carbon dioxide 
for the soil water; (3) it furnishes the food for the micro- 
organisms which help to decompose the soil minerals; 
(4) it is the source of the acidity of soils. Each of 
these points is so important that it is worthy of more 
lengthy consideration. 

The nitrogen of soils is not found in the minerals, for 
there are practically no nitrogen-containing minerals in 
our soils. The residues of the plant and animal bodies 
that are returned to the soil contain the nitrogen for the 
succeeding crops. This nitrogen is in a multitude of dif- 
ferent compounds, because all the compounds of nitrogen 
in the roots and stems of plants, in the bodies of insects 
and earthworms, in the packing house by-products used 
as fertilizers, in the urine and faeces of farm animals, are 
presenl in the soil; and on these compounds the bacteria 
Bel to work to produce humus. In feeding on these mate- 
rials the bacteria produce still other compounds, among 



ASSISTING NITRIFICATION 173 

the most important of which are carbon dioxide, acids, 
ammonia, and nitrates. The carbon dioxide is important 
in increasing the solvent power of soil water on minerals. 
The acids create the harmful effects noticed in "sour" 
soils. The ammonia and nitrates are compounds of nitro- 
gen, and as such are of first importance in feeding the 
growing plants. 

Nitrification. — Now, plants are very peculiar in their 
nitrogen nutrition. It is not sufficient that the compound 
of nitrogen simply be soluble in ivater; the nitrogen must 
be in the form of nitrates, or, ivith some plants, in the 
form of ammonia. This means that if a soil is to supply 
plenty of nitrogen to growing crops, the bacteria of the 
soil must be constantly busy converting the various kinds 
of humus nitrogen into nitrates. As soon as they fail to 
keep up the supply of nitrates, the crops begin to suffer 
nitrogen starvation. This process of forming nitrates out 
of the nitrogen compounds of plant and animal residues 
is called nitrification. The first step is usually ammonifi- 
cation. The ammonia is then converted into nitrates. 
The ease with which a nitrogen-containing material can be 
nitrified determines to a large degree its value as a fer- 
tilizer. For example, dried blood and manure are excel- 
lent nitrogenous fertilizers, because the soil bacteria can 
very quickly nitrify them; but ground leather and hair 
scrap, although high in nitrogen, are almost worthless as 
fertilizers, because it is years before they are completely 
nitrified. The above facts also serve to explain why salt- 
peter (sodium nitrate) is such a quick-acting fertilizer; it 
needs no modification in the soil, but is immediately util- 
ized by the plants. 

Assisting Nitrification. — Thus one of the most important 
chemical changes in soil is that brought about by the 
nitrifying bacteria. The farmer can assist this process 
by keeping the soil well supplied with nitrogenous organic 



174 CHEMICAL CHANGES L\ THE SOIL 

matter for the bacteria to act upon. Barnyard manure is 
one of the best and cheapest of such fertilizers. The roots 
and stubble of leguminous crops, such as alfalfa and 
clover, are also excellent sources of nitrogen. Some of 
the commoner nitrogenous commercial fertilizers will be 
discussed in the next chapter. Upon the physical condi- 
tion of the soil also depends largely the rate of nitrifica- 
tion. It is a process requiring oxygen; therefore good 
aeration is necessary. This can be secured by tillage and 
by keeping clay soil coagulated by means of limestone 
(p. 165). The latter also neutralizes any acidity, which is 
harmful to the nitrification process. 

Denitrification. — The opposite of the above process, 
denitrification, also takes place in the soils. And the con- 
ditions which favor denitrification are the opposite of 
those which favor nitrification. A cold, wet, sticky, non- 
aerated soil is very likely to have denitrification taking 
place. This process involves loss of nitrogen; the nitrates 
lose their oxygen, and the nitrogen is liberated as free 
nitrogen, and hence is of no further use to plants. By 
working for conditions which favor nitrification, a farmer 
is thus also preventing denitrification. 

Nitrogen Fixation. — It was indicated above that the 
principal source of nitrogen in soils is the nitrogenous 
compounds contained in the plant and animal bodies that 
decay in the soil, and in the manure and fertilizers that 
are added to the soil. Theie is, however, another very 
important source of nitrogen, and that is the uncombined 
nitrogen of the air. Although our ordinary crop plants 
demand nitrate nitrogen, and can make no use whatever 
of the nitrogen all around them in the air, there are certain 
kinds of bacteria which can take this atmospheric nitrogen 
and use it for building up their bodies. These are called 
nitrogen-fixing bacteria. There are two classes of them. 
The members of one class live in the humus of the soil, and 



NITROGEN FIXATION 



175 



being microscopic in size, are never seen and would not be 
known to. exist there, were it not for the increase in the 
percentage of nitrogen found by chemical analysis in soils 
richly supplied with them. The other class of nitrogen- 
fixing bacteria live on the roots of clover, alfalfa, beans, 
peas, and other plants of the legume group (Fig. 43). 




Fig. 43. — Effect of high nitrogen and of low nitrogen on legumes. The eowpeas on the 
right had a plentiful nitrogen supply; hence they developed no nodules of nitrogen-fixing 
bacteria on their roots. The eowpeas on the left had a scant nitrogen supply; they developed 
nodules, thus enabling them to draw upon the air for a great deal of their nitrogen. It is 
evident that for a legume to bring about the greatest increase in soil nitrogen the soil must 
be rather low in nitrogen to start with. (From Bulletin 230, Wis. Agric. Exp. Station.) 

They form nodules or lumps on the roots sometimes as 
large as peas, and are often prominent features of the root 
systems of these plants. The bacteria and the plant have 
a well-ordered system of cooperation. The plant gives 
the bacteria a place to live and furnishes them with certain 
mineral nutrients; in turn the bacteria absorb nitrogen 



170 



CHEMICAL CHANGES IN THE SOIL 



from the air, and manufacture it into compounds which 
they turn over to the plant for its use. In this way the 
plant obtains the nitrogen for its growth without drawing 
upon the supply of nitrogen in the soil. Then, when the 
stubble of this crop, as well as the manure resulting from 
the feeding of the crop to stock, is plowed into the soil and 
allowed to decay, the total nitrogen in the soil has been 
increased by the amount taken from the free nitrogen 
of the air. 

Importance of Legume Bacteria. — Let it be perfectly 
understood that these legume bacteria carry on an ex- 

Plants 



Animals 



Animals 




Soil -<r 




N in air 



Fig. 44. — Diagram showing the nitrogen cycles. The transformation of the free nitrogen 
of the air into compounds of nitrogen in legumes, and from the legumes to the nitrogen 
compounds in animals, in the soil, and finally in other plants, can be followed by means 

of the arrows. 

ceedingly important chemical reaction in the soil; and 
that it is a chemical reaction which is very much under 
the control of the farmer. The plant can get along without 
the bacteria on the roots if there are plenty of nitrates in 
the soil; but the soil does not gain in nitrogen thereby. 
By planting a legume crop, seeing to it that the proper 
bacteria are in the soil for infecting the roots, liming the 
soil if it is too acid for the proper growth of the bacteria, 
and then returning to the soil as much as possible of the 
manure from the crop, the farmer can very materially 
increase the store of nitrogen in his soil. Figure 44 shows 
graphically the interrelation of the nitrogen in air, soil, 
plants, and animals. 



INOCULATION FOR LEGUMES 



177 



Inoculation for Legumes. — Experience has shown that 
the same variety of bacterium does not inhabit all the 
legume plants ; hence a field that will develop nodules on 




Fig. 45. — Last step in preparing a seed-bed. The whole operation kills weeds, thoroughly 

mixes the soil with the manure and fertilizer that have been added, grinds up the debris 

from the previous crop, which is to make manure, and produces a dust mulch which is so 

necessary for the prevention of loss of water by evaporation. 

red clover will not necessarily develop on alfalfa or soy 
beans. It depends upon whether nodule-bearing alfalfa 
or soy beans have been grown on that field before. There- 
fore inoculation is often resorted to when the bacteria 
12 



178 CHEMICAL CHANGES IN THE SOIL 

for a given kind of legume are lacking in a field. The 
inoculation can be carried out either by obtaining some 
soil from a field that is known to contain the desired 
organisms, or by sending to the Department of Agricul- 
ture at Washington, or to some private company, for 
cultures. The seed is inoculated in either case ; the spe- 
cilic directions are obtained from any of the state agri- 
cultural experiment stations, or from the package in the 
case of the culture method. 

Soil Acidity. — Bacterial action on humus gives rise to 
various organic acids, which, if allowed to accumulate, 
produce the condition known as "sour" or acid soil. This 
seriously inhibits the growth of many crops, interferes 
with nitrification, and prevents the development of nitro- 
gen-fixing bacteria on legume roots. Therefore, this acid- 
ity must be remedied by neutralizing with finely-ground 
limestone. Thus limestone, besides neutralizing soil acid- 
ity, has other beneficial effects, such as furnishing calcium 
for plant food, assisting in nitrification by forming cal- 
cium nitrate from the nitric acid produced, and flocculat- 
ing or "loosening up" clay soils. Hence the spreading 
of ground limestone has become almost as common a 
farm operation as the spreading of manure. 

Cultivation and Chemical Changes. — Lastly, we must con- 
sider how mechanical treatment of soil can assist chemical 
changes. Plowing and cultivating keep soil in a pulver- 
ized, porous condition (Fig. 45). This allows free ex- 
change of gases between the soil and the atmosphere. And 
since oxygen is necessary in bringing about nitrification 
and in preventing denitrification, and since atmospheric 
nitrogen is necessary for the nitrogen-fixing bacteria, it 
will ho readily soon why thorough cultivation and aeration 
of the soil are necessary in the proper control of 
soil activities. 

Thus wo sec thai the soil is the scene of many well- 



LABORATORY EXPERIMENTS 179 

defined chemical changes. When the nature of these reac- 
tions, the conditions under which they take place, and 
their desirability or undesirability in the soil are under- 
stood, the management of the soil can be pursued more 
intelligently and more profitably. 

QUESTIONS 

1. What purpose. does carbon dioxide in the soil serve? 

2. What is the most important chemical element in humus? Why? 

3. What mechanical properties of humus are important in soils? 

4. Why is humus important in the soil chemically? 

5. What is nitrification? Of what use is it in soils? 

6. Explain fully how the nitrogen content of a soil can be increased by 

growing alfalfa. 

7. How can denitrification be prevented? 

8. Why is an acid soil undesirable? How can it be corrected? 

9. In what ways does cultivation assist in the chemical changes in the soil ? 

LABORATORY EXPERIMENTS 

59. To Show That Lime Flocculates Clay. — Mix about 20 g. of clay 
soil with water in a mortar to a thin cream. Pour this into a 200 c.c. cylinder 
of water, mix, and allow to stand. The clay remains suspended in the water 
while the other constituents settle out. Divide the suspension of clay into 
two portions in glass cylinders. To one cylinder add 0.5 g. of fresh quick- 
lime, and mix. Let the two cylinders stand for several days, shaking oc- 
casionally, and noting any change that takes place in the clay. When this 
flocculation takes place in clay soil, the latter loses much of its stickiness. 

60. To Show the Presence of Nitrogen in Soil. — (a) Grind together 
in a mortar a few grams each of sodium hydroxide with a similar quantity 
of flour, ground hay, or other plant or animal material. Place the mixture 
in a test tube, and across the opening of the test tube lay a damp piece of 
red litmus paper. Carefully heat the contents of the tube. The alkali de- 
composes the nitrogenous compounds of the flour, converting the nitrogen 
into ammonia. The ammonia affects the litmus paper and it may even 
be smelled. 

(b) Repeat the above test for nitrogen, using about 10 g. of rich loam 
soil and 1 g. of NaOH. What is the source of the nitrogenous substances 
of the soil? 



CHAPTER XIV 

MANURES AND FERTILIZERS 

Need of Fertilizers.— We saw in the last chapter that 
for a soil to be fertile and to remain fertile, the following 
conditions must hold true: 

1. The rainfall, temperature, and sunshine must 
be suitable. 

2. The soil must contain sufficient mineral plant-food 
elements in an available forai, and the supply of this 
available food must be maintained year after year. 

3. The mechanical condition must be good, for proper 
tillage, moisture-holding capacity, etc. 

4. The soil must not contain injurious chemical 
substances, nor microorganisms which will cause 
plant disea- 

It is obvious that the first is out of human control. 
The others, thanks to extensive and careful studies in soil 
science by the state and government experiment stations 
in this country and in Europe, are under human control, 
and this control is almost entirely chemical. Hence, we 
shall see that one of the greatest contributions that chemis- 
try has made to the practice of modern agriculture is in 
the maintenance of soil fertility and the rendering of 
infertile soils fertile. 

Manure is the general term applied to anything added 
to a soil to improve its fertility. It does not necessarily 
add plant food elements; it may correct the physical con- 
dition of the soil, or destroy a harmful constituent. This 
broad use of the term manure is an old one; at the present 
time we apply different names to the various classes of 
manures, as follows : 

180 



LOSS OF PLANT NUTRIENTS FROM THE FARM 181 

1. Barnyard manure is the excrement of farm animals 
plus the litter that is usually mixed with it. 

2. Green manure is a crop or portion of a crop which 
is plowed under while still green, to add humus to the soil. 

3. Commercial fertilizers are materials containing 
plant food elements, which are bought and sold on 
the markets. 

4. Soil amendments are substances added to soils to 
destroy harmful ingredients or to improve in some way 
the fertility, without adding plant food. 

1. Barnyard Manure. — The use of animal excrements to 
enrich the soil is as old as the practice of agriculture. In 
fact, the better and more permanent the agriculture prac- 
ticed by a given people, the more do we find that they 
use barnyard manure. Compare the history of agricul- 
ture in our New England States with that in China, for 
example. In these States, where farming has been carried 
on continuously for a hundred years or so without very 
careful attention to the return of manure to the soil, the 
soil is now "worked out," and so unproductive that in 
many places the farms have been abandoned. In China, 
a dense population is still supported on land that has been 
continuously cultivated for many hundreds, perhaps even 
thousands, of years ; and it is simply due to the fact that 
they have carefully conserved all animal and even human 
excrement and returned it to the soil. 

Loss of Plant Nutrients from the Farm. — Let us see why 
the careful utilization of barnyard manure is so intimately 
connected with the maintenance of soil fertility; let us 
especially see what the chemistry behind it is. 

We grow an acre of wheat. A good crop, according 
to the accompanying table, will remove from the soil about 
50 pounds of nitrogen, 9 of phosphorus, and 6 of sulfur. 
These amounts were taken from the available supply in 
the soil; hence chemical actior must convert an equal 



182 



MANURES AXD FERTILIZERS 



amount of the unavailable supply of these elements into 
available, and do bo year after year, if that soil is to 
continue producing good crops. If the grain is sold off 
the farm, and the straw is stacked up and burned, that 
much nitrogen, phosphorus, etc., is lost to that farm 
entirely. If, however, the grain and straw are fed, the 
excrement of the animals will contain almost the whole 
amount of these elements, and if the excrement is returned 
to the land without wastage, the soil will not suffer any 
appreciable loss by the growth and harvesting of this crop, 
and the next crop will not be so dependent upon the un- 
available supply in the soil, 

Table XI 

Amount of Plant Food Removed from the Soil by Various Crops, Expressed in 

Pounds Per Aere 





Dry 

weight 
of crops 


N 


P 


S 


K 


Ca 


Mg 


\lfalfa hay . . 


lbs. 

6000 
3700 
3000 
3300 

1500 
1800 


lbs. 

132 
97 
61 

46 

28 
14 


lbs. 

11.2 

11.2 

9.7 

9.4 

4.3 
3.6 


lbs. 

16.7 
6.1 

23.0 
1.1 

2.5 
2.2 


lbs. 

US 
67.2 
92.1 
64.5 

5.4 
24.7 


/6s. 

101 
63.4 

18.0 
2.4 

0.3 
7.5 


lbs. 

21 6 


Red clover hay 


14.9 


Turnin- tfl 


3.5 


Potatoes (tubers) 


3.7 


Corn (grain) 30 bu 


2.0 


Corn (stalks) 


3.3 






Total for corn 


3300 

1100 
2400 


42 

21 
14 


7.9 
4.3 


4.7 

1.7 
3.4 


30.1 
5.0 


7& 

0.4 
5.2 


5.3 


Wheat (grain) 20 bu 

Wheal (straw) 


1.4 

2.0 






Total for wheal 


3.500 


35 


,,s 


5.1 




5.6 


3.4 



Permanent fertility of a farm, therefore, is largely 
ndent upon, first, the keeping of stock on that farm, 
and second, tli- s i vation of the manure from that 

stock (Pig. 46), 

Composition of Manure. — What is a ton oi manure worth 
to the soil.' This depends, it may he said, mainly upon 



EFFECT OF KIND OF ANIMAL 



183 



two factors : the composition of the fresh manure, and the 
composition of the manure when it is plowed under the 
soil; for from the moment the excrement leaves the ani- 
mal, it is subject to a continuous series of chemical 
changes. Some of these changes are good, some are very 
bad ; and the extent to which these changes are controlled 




Fig. 46. — Effect of manure on corn grown on depleted soil. The unmanured plot (on the 
left) yielded 36 bushels per acre, the manured 62 bushels. Subsequent crops for two or 
three years will still show the benefits of this application of manure. (From Bui. 222, Purdue 
Agric. Exp. Station.) 

determines the measure of conservation practiced on a 
given farm. 

Effect of Kind of Animal.— -In Table XII are presented 
the analyses of the fresh manure (solid and liquid com- 
bined) of the various farm animals. 

The value was computed by assuming the values of 
35 cents, 9 cents, and 2,0 cents per pound of nitrogen, 
phosphoric acid and potash, respectively. These are 
conservative figures, based on the 1920 prices of these 
ingredients in commercial fertilizers. It is seen in the 
table that the water content of the manures is the deciding 



184 



MANURES AM) FERTILIZERS 



factor in their value; that the amount of water differs 
with tin* different animals; and that the nitrogen is the 
most prominent fertilizing constituent. Compared to 
commercial fertilizers, barnyard manure has a low value 
per ton because it is over three-fourths water. However, 
if we take $5.50 as the average value of the above manures 
at the present time, this is over twice the value assigned to 
manure in 1914. This is due to the enormous increase in 
the price of potash since the opening of the World War. 
The above values of manure include only the nitrogen, 
phosphorus, and potash, based on what they cost in com- 
mercial fertilizers ; it takes no account of the organic mat- 
ter in the manure, which forms humus in the soil, nor 
of the loosening effect of manure on heavy soil. A dollars- 
and-cents value cannot be assigned to these things, 
of course. 

Table XII 
Composition and Value of a Ton of the Various Farm Manures 

Pounds of 



Water 



Nitrogen, 
N 



Phosphoric Potash, 
acid, P2O3 K2O 



Value * 



Cow. . 
Pig... 
Horse 
Sheep . 
Hen.. 



1.540 
1460 
1400 
1280 
1100 



8.8 

9.0 

11.6 

16.6 

20.0 



3.2 
3.8 
5.6 
4.6 
16.0 



8.0 
12.0 
10.6 
13.4 

8.0 



4.96 
5.89 
6.68 
8.90 
10.04 



* Value computed on basis of 1920 prices; 35 cents a pound for nitrogen, 9 cents for 
phosphorus, and 20 cents for potash. 



Effect of Feed on Manure. — Now, the figures in the 
accompanying table show only how the kind of animal 
affects the composition of the manure. Two other factors, 
however, must be considered. One is the hind of feed, the 
other is the kind and nun, nut of bedding used. As regards 
the feed, the following general rule applies: The daily 
excrement (nrine pins feces) of animals contains the 



EFFECT OF BEDDING ON MANURE 



185 



same amount of fertilizing elements as their feed. This 
applies strictly, of course, only to those animals which 
are neither gaining nor losing in weight. Important ex- 
ceptions to the rule are the following: Young growing 
animals, which retain part of these elements to build up 
new tissue ; milch cows, which secrete these elements in the 
milk to a considerable extent; pregnant animals, which 
require these elements for the growing foetus; and hens 
laying eggs. We can say, in general, for all classes and 
conditions of farm animals, that four-fifths of the nitro- 
gen, phosphorus, and potash of the feed gets into the 
excrement. Therefore, if feeds are chosen which are 
richer in these materials, the resultant manures will also 
be richer. The accompanying table gives the value of the 
fertilizing constituents in some of the common feed- 
ing stuffs. 

Table XIII 

The Value of the Nitrogen, Phosphorus, and Potash in One Ton of Various 

Feeds and Litters 



Pounds of 



Nitrogen, 

N 



Phosphoric 
acid, P2O5 



Potash, 
K2O 



Value * 



Wheat middlings 
Corn (grain) .... 
Cottonseed-meal . 
Corn silage 

Whole milk 

Wheat straw .... 

Oat straw 

Sawdust 



lbs. 

52.6 
36.4 
13.5 

5.6 
10.0 
11.8 
12.4 

4.0 



lbs. 

19.0 
14.0 
57.6 
2.2 
3.0 
2.4 
4.0 
6.0 



lbs. 

12.6 

8.0 

17.4 

7.4 

3.0 

10.2 

24.8 

14.0 



$22.61 
15.60 
13.49 
3.53 
4.37 
6.38 
9.66 
4.74 



* Value computed on basis of 1920 prices; 35 cents a pound for nitrogen, 9 cents a pound 
for phosphoric acid, and 20 cents a pound for potash. 

Effect of Bedding on Manure. — As regards the effect of 
bedding on the composition of manure, it is obvious that 
the richer the bedding is in fertilizing elements and the 
more of it that is used, the greater will be the yearly manu- 
rial output of a farm. Table XIII contains data concern- 



MANURES AND FERTILIZERS 

_ he value of wheat straw, oat straw, and sawdust as 

litter. It must be remembered, in comparing ree, 

that the sawdust decays much more slowly than the others. 

Fermentation in Manure. — The fermentation proce— a 

in manure are brought about by the myriads of micro- 

_ nisms that are always present in the intestinal tracts 

of animals. Two general types of fermentation are recog- 

Bot, Iry, fermentation, also called tire- 

fanging, which takes place in dry manures, such as that 

of the h' se; 2 sold, or wet, fermentation, such as 

takes place in a compacted pile of wet manure, like that 

of the c 

It is well recognized that the first kind is undesira 
a great deal of the organic matter is destroyed during the 
fire-fanging, ai. isiderable loss :•: ammonia occurs. 

The latter is often recognized by its ode :ially in 

the urine of horses. The ammonia comes from the urea, 
rding to the following equation: 

- 2H : = NH« jCO, 

urea water ammonium carbonate 

The ammonium carbonate deconir - follows, giving 

off ammonia go - : 

= -xh, + HsO + t 

ammonium ammonia 

carbonate 

The loss of this valuable nitrogenous constituent can be 
prevented in the stable by scattering a little gypsum, or 
landpla- 3 I , in the 

ML fiO, - CkS0 4 = rain. - JNH, £ 

calcium ammonium 

carbonate sulfate 

The ammonium sul: s not volatile. 

Rotting of Manure. — The kind of manurial fennentation 
to be encour e a the wet type. The bacteria feed upon 



GREEN MANURES 187 

the substances of the manure ; they decompose the fibrous 
residues of the undigested food ; disintegrate the materials 
of the bedding; and change the various compounds of 
nitrogen, phosphorus, and other elements into forms which 
are available to plants. If air has access to the fermenting 
material, considerable heat may develop. The air should 
therefore be excluded, by keeping the piles closely com- 
pacted and rather wet. The deep stall method of conserv- 
ing manure, the mixing of the wet and the dry manures, 
the saving of all the liquid excrement, the use of water to 
keep the piles sufficiently wet, are all effective methods of 
securing well-rotted piles of manure with a minimum 
of waste. 

Losses of Manure. — Precaution to secure well- rotted 
manure is all for naught, unless the opportunities for 
wastage and loss are carefully guarded against. Thus, 
rain pelting over the pile washes away the soluble portioii 
of the manure, which is the portion most quickly available 
to plants; the running off of the liquid excrement is a 
direct loss of readily available plant f ood ; and the dump- 
ing of manure in little piles in the field results in 
44 spotted' ' effects in the next crop, and the failure to 
secure the most value from the fertilizer. All in all, the 
best possible practice in the handling of manure is to 
spread it on the fields fresh from the stables daily 
(Fig. 47). 

2. Green Manures. — These are crops planted for the 
purpose of being plowed into the soil while they are still 
green, in order to furnish easily-decayed humus-forming 
material to the soil. Usually they are legumes, although 
non-legumes, such as rye, are sometimes used. The econ- 
omy in using a legume is apparent, since it not only adds 
humus to the soil, but also adds the nitrogen which it 
absorbs from the air during its growth. Whole crops are 
plowed under for green manures only in those systems of 



188 



MANURES AND FERTILIZERS 



farming where the amount of stock kept is not sufficient 
to supply the needed manure. For it is an obvious waste 
to plow under feed crops which could better be fed and 
the manure returned to the soil. It was found at the 
Kothamsted Experiment Station in England that the roots 
and stubble alone of an acre of clover contain about 50 
pounds of nitrogen. 

3. Commercial Fertilizers. — These ordinarily are de- 




Fig. 47. — Manure carrier and manure spreader, two machines which facilitate the handling 
of manure. If manure can be hauled to the fields daily, all loss by leaching and by harmful 
fermentation is avoided. 

signed to supply but three plant-food elements — nitrogen, 
phosphorus, and potash. The raw materials are certain 
basic substances which usually contain but one of the 
fertilizing elements. Very often two or more of these are 
mixed and put on the market as " mixed' ' or "com- 
plete" fertilizers. 

Nitrogen Fertilizers. — The nitrogenous fertilizers most 
commonly used are Chile nitrate (sodium nitrate, or Chile 
saltpeter), ammonium sulfate, calcium nitrate, dried blood, 



PHOSPHORUS FERTILIZERS 189 

and fish scrap. The Chile nitrate is mined in Chile, where 
it occurs in enormous beds, and from which over a million 
tons a year of the fertilizer are obtained. It contains 
about 15 per cent of nitrogen. It is very soluble in water, 
and is, of course, already nitrified and ready for use by 
plants. Hence, its greatest use is in forcing greenhouse 
and truck crops, where it is applied in small amounts sev- 
eral times during the season in order to prevent leaching 
out by rains. 

Ammonium sulfate is a product of the gas works (p. 50) . 
It is very soluble in water and is readily nitrified. It 
contains from 20 to 23 per cent of nitrogen. 

Calcium nitrate, as we have seen (p. 128), is a manufac- 
tured product. It can be produced cheaply only where 
there is cheap electric power, which means abundant water 
power. Its development in this country is full of promise ; 
when we begin to utilize our many water-power sites for 
generating current, calcium nitrate is bound to become an 
inexpensive but very valuable fertilizer. It contains about 
13 per cent of nitrogen. 

Dried blood is a packing-house by-product containing 
from 10 to 14 per cent of nitrogen. It readily undergoes 
nitrification; hence it is largely used for forcing truck 
crops and greenhouse plants. 

Fish scrap is usually the residue left after extracting 
the oil from menhaden, although the residue from canning 
factories is made into fertilizer to a certain extent. It 
contains from 8 to 10 per cent of nitrogen, besides 4 to 5 
per cent of phosphoric acid. This fertilizer nitrifies 
nearly as readily as dried blood. 

Phosphorus Fertilizers. — The phosphorus fertilizers 
most commonly used are rock phosphate, acid phosphate, 
ground bones, and basic slag. The rock phosphate goes 
by the name Florida rock, Tennessee rock, etc., depending 
upon its source. It is insoluble in water, although when 



190 MANURES AND FERTILIZERS 

ground very fine it is rendered soluble by the action of 
carbonated water (p. 171). Hence the advisable practice 
is to add it to soil in connection with manure. It is essen- 
tially tri-calcium phosphate, Ca ;; (P0 4 ) 2 , and contains 
from 25 to 30 per cent of phosphoric acid. 

"When rock phosphate is treated with sulfuric aoid, 
mono-calcium phosphate, also called acid phosphate and 
super-phosphate, is formed: 



P0 4 ) a + 


2H a S0 4 


= CaH\(P0 4 » 2 + CaS0 4 


rock 




acid calcium 


phosphate 




phosphate sulfite 



This acid phosphate is soluble in water, and hence is a 
more quickly-acting fertilizer than the rock phosphate. It 
contains from 1-4 to 16 per cent phosphoric acid. The 
calcium sulfate formed in the above reaction is not re- 
moved from the phosphate; hence the fertilizer as it 
appears on the market contains both substances. In many 
instances the beneficial effects from the use of this fer- 
tilizer are due as much to the sulfate portion as to 
the phosphate. 

Ground bones are either "raw" or ^steamed. " The 
latter form is preferable in some ways, since the steaming 
extracts all fat and thus enables the material to be de- 
composed more readily in the soil. This material contains 
from 25 to 30 per cent of phosphoric acid in the form of 
tri-calcium phosphate, besides some nitrogen. 

Basic slag is a material arising from the removal of 
phosphorus and silicon in the making of iron and steel. 
ft contains from 15 to 20 per cent of phosphoric acid in 
an insoluble form. However, if it is very finely ground, 
it readily becomes soluble in the soil by the action of salts 
and of carbon dioxide. 

Potassium Fertilizers. — Up to the opening of the World 
War the greater portion of the world's potash fertilizers 



SOIL AMENDMENTS 191 

came from the Stassfurt mines of Germany. These mines 
are immense deposits of water-soluble potassium and 
magnesium salts, from which several different fertilizing 
materials are drawn. The muriate, or chloride, KC1 ; the 
sulfate, K ? S0 4 ; and kainit, K 2 S0 4 .MgS0 4 .MgCl 2 .6H 2 O, 
are the principal ones. The first two are the most con- 
centrated, averaging nearly 50 per cent of potash. Kainit 
is a crude salt mixture, usually containing not over 13 per 
cent potash. 

American Sources of Potash. — When the importation of 
Stassfurt potash ceased, the fertilizer chemists of Amer- 
ica had to make a careful inquiry into all the potassium 
possibilities on this side of the Atlantic. After several 
years of effort, there are now being placed on the market 
potash salts from a variety of sources. One of them is the 
giant sea-weeds of the Pacific coast. These are raked out 
of the water, fermented in huge tanks, and then the potash, 
together with several other by-products, is recovered from, 
the liquor as potassium chloride. Another source of potas- 
sium is a by-product in the manufacture of Portland 
cement, where feldspars high in potash are used as raw 
material. At Searles Lake, California, there are immense 
deposits of salts of various kinds, partly crystalline and 
partly in a strong brine. This brine is pumped out into 
tanks, evaporated, freed from the bulk of its sodium chlo- 
ride by crystallization, and then evaporated to dryness. 
This product contains about 75 per cent potassium chlo- 
ride. There are 30,000,000 tony of this salt available 
in this lake. 

Wood ashes are a not insignificant potash fertilizer. 
Unleached hardwood ashes contain as high as 8 per cent 
of potash in the form of carbonate. 

4. Soil Amendments. — Under this head, lime in various 
forms is about the only substance used in this country. 
As was stated in the chapter on soils, ground limestone 



192 



MANURES AND FERTILIZERS 



is often added to soils to neutralize excess acidity, since 
most crops thrive best in a neutral soil. The limestone 
also tends to make sticky clay soils more loose and easier 
to work, while on light, sandy soils it apparently has oppo- 
site effects. Quicklime, CaO, is often recommended in 
place of ground limestone. Since it is caustic, it cannot be 
applied when any vegetation is likely to be injured by it. 
And since, as we learned in our study of the chemistry of 
calcium compounds, calcium oxide is soon converted into 




Fig. 48. — Efficiency of limestone of different degrees of fineness. The more finely it is 
ground, the more intimately it can be mixed with the soil, and the more quickly will it neu- 
tralize acidity and improve the crop yield. The quicklime (on the left) slacks to a very 
fine powder. This is all that is gained by using quicklime instead of ground limestone. 
(From Bui. 152, Pa. Agric Exp. Station.) 

the hydroxide by moisture, and the hydroxide is very 
quickly converted to the carbonate by the carbon dioxide 
of the air, it is obvious that very little can be gained 
in speed of action or in total action by the use of quick- 
lime, provided that the limestone used be of good quality 
and very finely ground (Fig. 48). In neutralizing power, 
a ton of quicklime is equivalent to about two tons 
of limestone. 

Fertilizer Terms. — It is very unfortunate that a loose 
system of terms has come into use in the fertilizer trade, 
in respect to the different forms of nitrogen, phosphorus. 



MIXED FERTILIZERS 193 

and potash. It may be well to point out the terms for each 
of these elements and their real significance. 

The stated analysis of nitrogen fertilizers should con- 
sist of the per cent of N, together with a statement as to 
the form of nitrogen, whether nitrate, ammonia, or organic 
(as in dried blood and fish scrap) . However, the nitrogen 
figure is often computed to the ammonia (NH 3 ) basis, and 
given as the percentage of ammonia present, whereas 
there may be no ammonia nitrogen in it. The ammonia 
figure is 17/14 of the nitrogen figure ; hence it gives a mis- 
leading idea as to the composition of the fertilizer. Again, 
the same figure may be stated in two different forms : 
as, "per cent of nitrogen, 8; ammonia equivalent, 9.7"; 
and many purchasers believe that they are getting both, 
or a total of 17.7 per cent of fertilizing constituents. 

The term "potash" in fertilizer nomenclature almost 
invariably refers to K 2 0. This potassium oxide never 
occurs in any fertilizer; but it has become customary to 
figure the amount of K present in terms of K 2 0, and then 
to speak of it as potash instead of potassium. The actual 
compound of potassium present should be stated. 

In the phosphate fertilizers, the phosphorus is com- 
puted as P 2 5 instead of P, and is called phosphoric acid. 
In reality it is phosphorus pentoxide, or phosphorus anhy- 
dride. It is well to know that all of these terms mean the 
same. The kind of phosphorus compound involved should 
be stated, so that the purchasers may know something of 
its availability to plants. 

Mixed Fertilizers. — Any one of the commercial fertil- 
izers discussed above may be purchased singly, and used 
alone or in conjunction with barnyard manure. Most of 
the fertilizers sold, however, are "mixed" or "complete" 
fertilizers, and contain all three fertilizing elements. 
Their composition is stated in the form of three figures, 
as 3 — 8 — 5, which signifies 3 per cent of nitrogen, 8 per 

13 



194 MANURES AND FERTILIZERS 

cent of phosphoric acid, and 5 per cent of potash. The 
farmer can buy the individual fertilizers and mix them 
himself. This has the advantage of being somewhat 
cheaper and of giving a fertilizer of known composition. 
The disadvantages are, that the single fertilizers cannot 
always be bought on the market, great care is necessary 
to secure thorough mixing, and an intimate knowledge 
of the character of the materials to be mixed is necessary, 
else combinations may be used which will react with each 
other chemically and result in loss of ammonia or in 
the formation of insoluble phosphorus and potas- 
sium compounds. 

Choice of Fertilizers. — One of the first questions that 
confronts a farmer in his endeavor to produce maximum 
yields of crops is, will fertilizers pay? If so, what should 
be used! As was pointed out in the chapter on soils, a 
chemical analysis gives but a general idea of the nature 
of the fertilizer requirements. A far surer way is to 
establish fertilizer plots on the most typical soil type 
of a farm, and to try out the various fertilizer elements 
singly and in combination, on one or more main crops. 
Usually it is advisable to apply ground limestone to all 
plots, as often the possible effect of fertilizer will fail to 
appear because of the reaction of the soil. Control plots 
receiving no fertilizer must of course be kept; and the 
crops from each plot should be accurately determined by 
weight, so that any difference in yield can be recognized 
on plots as small as one-tenth or one-twentieth acre. This 
method requires time and labor; but it gives accurate 
information as to the efficiency of fertilizers on that farm 
for those particular crops. A convenient system of plots, 
together with the amount and kind of fertilizer to add to 
each, is given in the accompanying table. Each plot is one 
rod wide and eight rods long, containing one-twentieth 
of an acre. 



SYSTEMS OF FERTILIZATION 

Table XIV 

Plan for Fertilizer Test Plots 



195 



Plot No. 


Kind of fertilizing 
element 


Plant food applied 


1 


None 


None. 


2 


N 


Dried blood, 30 lbs. 


3 


P 


Acid phosphate, 15 lbs. 


4 


K 


Potassium sulfate, 15 lbs. 


5 


None 


None. 


6 


N, P, and K 


Blood, phosphate, and sulfate. 


7 


NandP 


Blood and phosphate. 
Sulfate and phosphate. 


8 


KandP 


9 


NandK 


Blood and sulfate. 


10 


None 


None. 



Specific Effect of Fertilizers. — In a general way, nitrog- 
enous fertilizers favor the development of stem and 
leaves; phosphorus develops the fruit and pods; and 
potassium, the roots and stems. Thus, nitrogen fertilizers 
are particularly effective on truck crops such as lettuce, 
onions, cabbage, and rhubarb, and on hay crops and 
meadows. Phosphorus fertilizers are usually applied to 
the cereals and to corn, while potassium is usually very 
effective on tobacco, potatoes, and root crops (Fig. 49). 
However, so much depends upon the particular soil in- 
volved that the above statements are only generalities. 
Deficiency in nitrogen is usually indicated by a light green 
or even yellowish color of the leaves, and underdeveloped 
leaf and stem parts. Delayed maturity, and undersized 
seeds, usually mean too little available phosphorus. 

Systems of Fertilization. — Several well-defined systems 
for applying fertilizers have been suggested, and prac- 
ticed to a certain extent. The Ville system depends upon 
the assumption that crops can be divided into three 
groups, each group being particularly in need of an excess 
of one fertilizing element. Thus nitrogen should be the 
dominant element in fertilizers for wheat, rye, oats, bar- 



196 



MANURES AND FERTILIZERS 










43 3 
.® 3 



Cos 
C u 






4= "> 

si 



.2 a 

5 3 

a> o 

B . 

o -^ 



QUESTIONS 197 

ley, grass, and beets; phosphorus for turnips, corn, sor- 
ghum, and sugar-cane ; and potash for peas, beans, clover, 
flax, j^otatoes, and tobacco. This system is of considerable 
help in choosing fertilizers for intensive operations when 
there is a reasonably good supply of all other elements 
of fertility. 

The Wagner system assumes that nitrogen is the only 
critical element in soil fertility, because it is found in soils 
in very small amounts, is easily leached out, and is expen- 
sive to buy in fertilizers. Hence, phosphorus and potash 
are supplied in reasonable amounts to all crops, and then 
nitrogen supplied at frequent intervals in readily available 
forms, such as ammonium sulfate or sodium nitrate. This 
system implies relatively cheap phosphorus and potassium 
fertilizers, so that they can be present at all times in more 
than necessary quantities. Like the Ville system, this one 
would pay only when intensive agriculture is practiced. 

The money crop system involves applying all the fer- 
tilizer to that crop in the rotation which is sold from the 
farm, in order that the maximum effect of the outlay for 
fertilizer may be had as a cash return. The unused por- 
tion of the fertilizer goes to feed the succeeding crops. 
This in general is the system followed in this country. 

QUESTIONS 

1. What are the main conditions on which soil fertility depends? Which 

of these are under the control of the farmer ? 

2. Xame the four classes of substances that are added to soils to improve 

their fertility, and state the purpose of each class. 

3. Why is barnyard manure the best all-round material for increasing soil 

fertility? Xame three different tilings that it does for the soil. 

4. Why is a ton of sheep manure more valuable than a ton of cow manure? 

5. What is the most important plant food element in manure? Why 

(three reasons) ? 

6. Explain why stock must be kept on a farm if the soil fertility is to be 

maintained year after year. 

7. Explain how the kind of feed and the kind and age of the animal affect 

the composition of the manure. 

8. What is the effect of fire-f anging ? 



198 MANURES AND FERTILIZERS 

9. Why does manure ferment and rot so readily? 

10. Explain fully why legumes are the best green manures. 

11. Make a table giving the principal kinds of nitrogenous, phosphatic. and 

potassic fertilizers, the source of each, and the percentages of plant 
food elements. 

12. State three ways in which limestone may improve the fertility of a soil. 

13. By means of the various tables in this chapter, compute the amount of 

nitrogen, phosphorus, and potash in the manure produced in one year 
on a farm stocked with 6 horses, 4 full-grown hogs, 16 pigs, and 100 
hens. Assume that ( 1 i all of the manure is left on the farm and is 
hauled to the field without loss; (2) wheat straw is used, for bedding, 
allowing 5 pounds per day for each horse, and 2 pounds for each hog ; 
(3) each hen produces 140 pounds of manure a year. 

14. 'What is a single fertilizer? A complete fertilizer? When is it economy 

to use each ? 

15. How is nitrogen starvation shown in the appearance of a plant? 

16. Discuss briefly the principal systems followed in the use of com- 

mercial fertilizers. 

17. Why cannot fertilizers take the place of barnyard manure entirely? 

LABORATORY EXPERIMENTS 

6i. To Show the Presence of Nitrogen in Manure and Fertilizers. — 
Use the test for nitrogen described in experiment 60, on dry manure, dried 
blood, ammonium sulfate, sodium nitrate, rock phosphate, and " muriate of 
potash" (potassium chloride). Why did not the saltpeter give the test! 
Which of the above fertilizers are nitrogenous? 

62. To Show the Solubility of Rock Phosphate. — Suspend 2 g. of 
finely ground rock phosphate in 20 c.c. of water. Divide into two test tubes. 
Bubble C0 2 through one test tube, and allow the other to stand meanwhile, 
with occasional snaking. Then test for the amount of dissolved material, 
as was done in experiment 13. Test each filtrate for phosphorus. How does 
an abundance of humus in soil aid in the solution of rock phosphate? 

63. To Prepare Acid Phosphate. — Thoroughly mix 10 g. of bone ash 
or ground rock phosphate with 6 c.c. of concentrated sulfuric acid and let 
stand on a piece of wood for two or three days. How has the mass changed? 
What does it consist of? Grind it up and test its solubility, comparing it 
with that of the rock phosphate in experiment 62. 

Ca 3 (P0 4 ) 2 + 2H 2 S0 4 = CaH 4 (P0 4 > 2 + 2CaS0 4 
tricaleium monocalcium 

phosphate phosphate 

( bone ash ) ( acid phosphate 1 

64. To Study Wet and Dry Ferm,entation of Manure. — Fill a one pint 
Mason jar half full of loosely packed fresh horse manure. Half fill another 
jar with the manure packed down tightly and moistened with additional 
water. From the cover of each jar suspend a moist strip of red litmus 
paper. Stand in a warm place, noting any difference in temperature be- 
tween the two jars, and any difference in the tint of the litmus paper. Dis- 
cuss the difference in the chemical changes taking place in the two jars. 



CHAPTER XV 

THE PLANT BODY 

Importance of Plants. — We have already mentioned the 
fact that probably the first forms of life to appear on the 
earth were simple plants. It is reasonable to think that 
this was the case, since how could animals live, unless 
plants were there for them to feed on? At the present 
time plant life is the basis for all animal life, including 
even the complex life of human civilization. Let us enu- 
merate some of the ways in which we are dependent on 
plants in our everyday life. 

1. Coal, which furnishes the greater part of the energy 
of our factories, locomotives, and boats, and supplies 
our buildings with heat, is the product of the decay of 
luxuriant plant life that once flourished on the earth. 

2. It is probable that our petroleum and natural gas 
also had an origin in plant products. 

3. Our clothing comes mostly from the cotton and the 
flax plant. The fabrics which have an animal origin, such 
as wool and silk, come from plants indirectly, since the 
sheep and the silkworm feed on plants. 

4. Our food is really all from plant sources, for while 
part of it is the meat and milk and fat of animal bodies, 
the animals had to eat great quantities of plant material 
to produce these products. 

5. All of our paper is plant material, mostly from 
wood, straw, and flax. 

6. The lumber of our buildings, cars, and ships is 
from plants. 

In view of these facts, then, it will be readily agreed 
that the primary business of agriculture is the production 

199 



200 



THE PLANT BODY 



of crops, and that the production of animals is only sec- 
ondary. AW' have discussed the chemistry of the soil and 
the air, which are the sources of the raw materials for 
plants. We have next to study the chemical make-up of 
plants and of animals, and the processes by which the 
plant, animal, and mineral substances are converted into 
our various manufactured products. 

Raw Materials in Soil and Air. — We have seen in previous 
chapters that the plant is composed of some twelve or 
fourteen chemical elements combined in a large number of 




NatK.Ca.tlQ, 
P.CI.S'r.HiO 



Fig. 50. — Diagram of a green plant, showing its relations to the supplies of raw materials 

of the air and soil which it uses in building up its tissues. 

different compounds; that the plant draws upon the soil 
and the air for its supply of these elements; that the 
nutrient minerals of the soil are carried into the plant by 
means of m ter and that hence they must be soluble in 
water; thai the carbon dioxide of the air furnishes all the 
carbon of the plant; and that this carbon dioxide enters 



IMPORTANCE OF WATER 201 

the plant through the minute pores in the leaves, 
called stomates. 

Processes in the Plant. — Figure 50 is a simple diagram 
to show the processes in the plant factory. In the chapter 
on carbon we found that the carbon dioxide is taken into 
the tissues of the leaf, the carbon combined with water to 
form starch, and the oxygen again given off from the leaf 
as a waste product. This chemical change is indicated 
in the diagram by C0 2 entering the leaf and issuing 
from it. 

Importance of Water. — Water is shown both entering 
the roots and evaporating from the leaves. This indicates 
that more of it enters the plant than is required in the 
tissues, and that hence the excess must be eliminated. 
This passage of water through the plant is called trans- 
piration. As a matter of fact, an enormous quantity of 
water passes up through a plant and out into the air 
again. For every plant there appears to be a minimum 
amount of water which is required during the growing 
season in order for the plant to attain a vigorous mature 
development. This ivater requirement of some of our 
cultivated crops is shown in the following table: 

Table XV 
Water Requirement of Some Common Plants 
Pounds of water transpired for each pound of dry matter produced 

Western wheat grass 1,070 Potato 640 

Western ragweed 950 Oats 600 

Flax 900 Barley 530 

Alfalfa 830 Wheat 510 

Red clover 800 Corn 370 

Pumpkin 790 Sorghum 320 

Cotton 640 Millet 310 

These figures mean that for every pound of dry matter 
produced by alfalfa plants, 830 pounds of water had to 
be absorbed from the soil. The total water transpired 
from an acre of crops is thus very large. It will be 



202 THE PLANT BODY 

noticed that sorghum, one of our most drought-resisting 
plants, has one of the lowest water requirements; and 
that the opposite is true of the legumes, which are very 
dependent on an adequate water supply. Marsh plants 
have the highest, and desert plants have the lowest, rate 
of transpiration. 

It has been demonstrated many times that more water 
is taken from an acre of soil when it is covered with 
growing plants than when it lies fallow. In other words, 
transpiration is much more rapid than evaporation from 
bare soil. This explains the practice in some dry- farming 
regions of allowing the land to lie fallow every other year; 
the rain water is better retained in the soil when there is 
no crop to use it up. 

The Plant Factory. — We must look upon the plant as a 
chemical factory. And it is a most efficient and remark- 
able factory, too. As we have seen, the primary chemical 
reaction that is brought about by green plants is the 
formation of starch from carbon dioxide and water. The 
plant does this quietly and unpretentiously, without any 
outward manifestation except a slow growth of the various 
organs of the plant. And man, in spite of all his progress 
in manufacturing the substances of nature, in spite of his 
powerful chemicals, electric currents, high temperature, 
and machinery, has never yet succeeded in forming starch 
from carbon dioxide and water. Therefore we must culti- 
vate crops which will do this for us. 

And why is the manufacture of starch so important f 
In the first place, when a plant has once made some starch, 
it can convert it into the various other substances that go 
to make up its body, such as the fats, sugars, acids, and 
coloring matters. In the second place, starch is an im- 
portant human food. In the third place, we can feed it 
to animals and they will convert it into the various animal 
food products. Therefore, we must appreciate the plant 



PHOTOSYNTHESIS 203 

factory which makes such large quantities of this raw 
material, starch, out of such plentiful substances as carbon 
dioxide and water. 

Photosynthesis. — TTe have learned before that the above 
process in plants is called photosynthesis, which means 
•'manufacturing by means of light." Light, however, is 
not the only requirement. The following conditions must 
obtain before photosynthesis can take place : 

1. The plant must be living. Dead cells, even though 




Fig. 51. — A common fungus. The fungi (commonly called toadstools and mushrooms) 
form a group of plants which do not contain chlorophyll; hence they cannot manufacture 
their own food out of water and the carbon dioxide of the air. Therefore they live on the 
living or dead tissues of other plants, and get their nourishment from them. When they 
live on living plants, we speak of them as plant diseases. Thus fungi cause such diseases 
as the rusts, the mildews, the smuts, late blight of potatoes, chestnut blight, brown rot of 
peaches, and cabbage wilt. Large species of fungi like the one in the illustration are most 
excellent human foods, although some are poisonous. (From Bui. 175, U. S. Dept. of 

Agriculture.) 

they are supplied with all the following conditions, can- 
not manufacture starch. 

2. The plant must be a green plant ; that is, its cells and 
tissues must contain the green coloring matter called 
chlorophyll. Thus tubers and roots, the bark of trees, 
ripe seeds, and mushrooms and yeast, are incapable 
of photosynthesis (Fig. 51). 

3. The plant must have a plentiful water supply, for 
several reasons : First, because water is needed to com- 
bine with carbon dioxide to form starch; second, because 
when a plant is suffering for water, the pores in the leaves 



204 THE PLANT BODY 

- «L and carbon dioxide from the air cannot get 

into the leaf: and third, because all the mineral material 
- brought into the plant in solution in water. 

4. There must be a proper temperature. Photosyn- 
thesis, as well as many other chemical reactions in plants, 
practically ceases at So or 4€ degrees F. On the other 
hand, too high a temperature is detrimental. 

5. The plant must have sunlight. Some plants can 
thrive in indirect light, in shaded places, but practically 
all of our crop plants require direct sunlight. At night, 
photosynthesis ceases. Crops can mature in our northern 
latitudes principally because the daylight hours are 
longer, thus enabling the plan:- : obtain the necessary 
amount of sunlight in a shorter growing season. Light is 
a form of energy just as heat and electricity are. Plants, 
in some way not very well understood, can utilize sunlight 
as a source of energy for carrying out the manufacturing 

iss of photosynthesis. 
If any om - Ik s s 

I " " ■ . - • 
Chemical Compounds in Plants. — We must now take up 

the systematic study of the various substances that g 
make up the bodies of plants. The accompanying table 
scheme to show a classification of these substances. 
_ ther with the chemical elements of which they are 
composed. avenience they are first grouped as 

water and dry matl the dry matter one port:* 

combustible, and another portion is not, being left behind 
ah. It has been pointed out before that the most 
abundant element in the dry matter oi plants is carbon; 
in th< outline by far the gp rt oi th< 

■a in the combustible portion, although a little 
appears in the ash in the form of carbonates. For con- 
venience tl.- _ substances are divided into two 
grou] 3j - containing nitrogen and those without. 



CHEMICAL COMPOUNDS IN PLANTS 



205 





Table XVI 




An Outline of the Compounds Found in Plants 


Water 


fl. Carbohydrates 
!2. Fats 


HandO 




' Non-nitrogenous 


<S. Plant acids 




C, H and 


|4. Volatile oils 
[5. Coloring matter 




Organic or combustible 








matter 








C, H, 0, N, S 




f6. Proteins 


Dry matter • 




Nitrogenous 


•J7. Amides 




Mineral matter or ash 


C, H, 0, N, S 


[8. Alkaloids 




Salts of Na, K, Ca, Mg, 






Fe, Al, P, S, C, Si, 






and CI 





In the green plant, ivater occupies a very large propor- 
tion of the total weight. Lettuce and celery often consist 
of from 92 to 94 per cent water; potatoes and roots, 85 
to 90 per cent ; the driest hay and straw contain at least 
8 per cent of moisture ; and even wheat flour has 10 per 
cent. The water is not only the medium for bringing 
food into the plant from the soil, but it distends the indi- 
vidual plant cells, and thus keeps the plant organs firm 
and rigid. The familiar wilting of succulent plants shows 
the effect of insufficient water on the turgidity of leaves. 

1. The carbohydrates are a very widely distributed 
group of compounds found in both plants and animals. 
They are classified into sub-groups as follows : 



a. Pentoses, of the formula C 5 H 10 5 

b. Hexoses, of the formula C 6 H 12 B 

c. Di-hexoses of the formula C 12 H 22 O n 

d. Poly-hexoses of the formula (C 6 H 10 5 )x 

It will be noticed from the formulas that each carbo- 
hydrate is composed of carbon, together with hydrogen 
and oxygen in the proportion of 2 to 1, as in water. Thus, 
the pentoses consist of 5 atoms of carbon combined with 
5 molecules of water. Hence the name carbohvdrate. 



20G THE PLANT BODY 

These constituents can be demonstrated by placing some 
sugar in a test tube and slowly heating it. Water is given 
off, and condenses on the sides of the tube, while the 
residue gets blacker and blacker, due to the carbon liber- 
ated. Pure carbon for making artificial diamonds is 
obtained by roasting pure cane sugar until it is com- 
pletely decomposed and all the water is driven off. The 
water is, of course, chemically combined with the carbon ; 
man cannot bring about this combination by chemical 
means, but the plant can by the process of photosynthesis, 
discussed in previous pages. 

a. The pentoses are the simplest natural sugars. They 
are found in the gums which exude from cherry, apple, and 
spruce trees ; in gum arabic ; in straw and hay to the extent 
of 20 to 30 per cent; in wheat-bran to the extent of 24 
per cent; and in all fruits and vegetables in small 
amounts. They are fairly well digested and assimilated 
by animals, but it is doubtful whether they are of much 
use to the human system. The pentoses contain five 
carbon atoms in the molecule, hence the prefix pent. 

b. The hexoses, or monosaccharides, contain six car- 
bon atoms combined with six molecules of water, as their 
formulas indicate. The commonest members of this group 
of carbohydrates are the three sugars, levulose, dextrose, 
and galactose. These sugars all have the same chemical 
formula, C ti H ]2 6 ; but they are entirely different from 
each other in sweetness and in other characteristics. The 
explanation of so many different substances having the 
same formula is, that although there are the same number 
of atoms of carbon, hydrogen, and oxygen in each, these 
atoms are arranged differently, and hence give different 
structures to the molecules. It is the same as if three 
dog-houses were built each with the same number of 
b ricks and boards, but each having a different shape 
and appearance. 



CHEMICAL COMPOUNDS IN PLANTS 



207 



Levulose, also called fructose and fruit sugar, is found 
in practically all fruits and is especially abundant in 
honey. It is the sweetest of all sugars, which fact ex- 
plains the intense sweetness of honey. 

Dextrose, also called glucose and grape sugar, is found 
in at least small amounts in practically all plants; it is 




Fig. 52. — A field of sugar cane ready to harvest. The cane is ripe in this country after 

about 11 or 12 months' growth. The leaves are stripped from the stalks by hand, the stalks 

cut with a heavy knife, and then hauled to the mill for pressing (Copyrighted, Underwood 

and Underwood, N. Y.) 

especially abundant in fruits and in sweet corn, and is the 
only sugar found in the blood and muscles of animals. It 
is about two-thirds as sweet as cane sugar. 

Galactose is not found as such in nature, but is one of 
the constituents of milk sugar, as will be seen under 
that heading. 



208 



THE PLANT BODY 



c. The dihexoses or disaccharides, as the name im- 
plies, contain twice the number of carbon atoms that the 
bexoses contain. Here again the same formula, CjoHooOn, 
applies to three different sugars — sucrose, lactose, and 
maltose — each differing from the other 
in sweetness, solubility, etc. 

Sucrose, also called saccharose, is 
our most familiar and common sugar. 
Granulated sugar, from either beet or 
cane, is pure sucrose. Maple sugar is 
also sucrose, but contains certain im- 
purities which give it its delightful 
flavor. "Brown sugar" is cane sugar 
that has not been completely purified. 
The sugar crystals that settle out from 
sorghum syrup are sucrose. Besides 
occurring to the extent of about 15 to 
18 per cent in sugar cane (Fig. 52) 
and in sugar beets (Figs. 53 and 54) 
and about 12 per cent in sorghum, it is 
found in lesser amounts in sweet corn, 
sweet potatoes, watermelons, and in 
practically all fruits. 

The production and manufacture 
of granulated sugar constitute one of 
our greatest industries. In normal 
times there are consumed in the United 
States alone something over 85 
pounds of sugar for each man, woman, 
and child, or about 7 pounds per capita per month. AVhen, 
during the World Wax, this was reduced to 2 pounds we 
were bo accustomed to unlimited amounts of sugar, candy. 
ice cream, and other confections, that we found it difficult 
to adjust ourselves to the change, and to adopt other more 
available sugars for our source of sweets. 




Fig. 53. — Diagram of sugar- 
beet, showing the sugar con- 
tent of the different sections 
of the root. In the begin- 
ning of the beet sugar indus- 
try, the average sugar con- 
tent was about 9 per cent; 
plant breeders have now 
developed them to yield an 
avf-rajre of over 16 per cent. 
(From Circular 34, Utah 
Agric. Exp. Station.) 



CHEMICAL COMPOUNDS IN PLANTS 



209 



In the manufacture of cane sugar, the juice is ex- 
pressed between a series of heavy rollers, and then clari- 
fied and purified to free it from coloring matter and from 
other non-sugar substances. Charcoal and sulfur dioxide 
are important agents for these purposes (pages 64 and 
136). The clarified juice is 'then evaporated to a syrup. 
"When this syrup reaches the proper consistency, the 



-rf^iiUW. '-U' 







Fig. 54. — Sugar-beet field and beet sugar factory. The sugar-beet is a strong rival of sugar- 
cane in producing the world's supply of sugar, although the beet has been cultivated for 
this purpose for comparatively few years. In the beet sugar industry the work of the chemist 
begins in the field with the selection of the best roots for seed stock, and ends in the factory, 
when the greatest possible amount of crystallized sugar has been recovered from the roots 
and the pulp and molasses have been converted into stock feeds. (Courtesy of the director 
of the Utah Agric. Exp. Station.) — 



sucrose crystallizes out. The mass of crystals and mo- 
lasses is placed in a centrifugal machine. This consists 
of a perforated drum revolving rapidly inside of another 
drum. The force of the whirling tub throws the molasses 
out through the perforations, leaving; the crystals of 
sucrose behind. When these are washed, dried, and 
sacked, the granulated sugar is ready for the market. 
A second crop of crystals is usually obtained from the 
u 



210 THE PLANT BODY 

molasses and then the final molasses is sold for human 
food or made into stock feeds. 

The manufacture of beet sugar is similar to the above, 
except that the beets have to be washed, cut into thin 
slices, and then loaded into huge tanks, where the sugar 
is extracted by soaking in warm water. This water solu- 
tion of the sugar, containing also non-sugar impurities, 
is put through a process similar to that of the cane juice. 
The extracted pulp as well as the molasses is used for 
stock feed. 

Lactose, called also milk sugar, is the carbohydrate 
found in milk to the extent of about 5 to 6 per cent. It is 
not found in the plant world. It is less sweet than sucrose. 

Maltose, or malt sugar, is the sugar found in malted or 
sprouted grain. It occurs in only small amounts before 
germination; but during the latter process the starch is 
converted into maltose. 

d. The polyhexoses, or polysaccharides, are so called 
because their molecules are made up of a large number of 
molecules of hexoses combined with the elimination of a 
molecule of water. Thus the formula (C 6 H 10 O 5 )x means 
that an unknown, or x number of molecules of hexoses, 
each one minus a molecule of water, have combined to form 
a polyhexose. All the mono- and di-hexoses are sugars, 
and thus have a sweet taste and form crystals. The poly- 
hexoses have no particular taste and do not crystallize. 
The commonest polysaccharides are starch, dextrin, gly- 
cogen, and cellulose. 

Starch occurs very abundantly in the plant kingdom; 
it is the commonest form in which plants store up a 
reserve supply of carbohydrate for the use of the seedling 
plant the next year. Thus, practically all seeds, tubers, 
and roots contain starch. It is found in these organs in 
the form of minute grains of characteristic size and shape. 
These grains are insoluble in cold water; but on boiling 



RELATION OF THE CARBOHYDRATES TO EACH OTHER 211 

they swell up and form the familiar starch paste. Raw 
starch is digested with great difficulty by the human sys- 
tem, but readily by animals. Cooked starch, however, 
either as pure starch or as it occurs in grains and tubers, 
is readily digested and constitutes our most important 
carbohydrate food. 

Dextrin is formed by heating starch above the boiling- 
point of water. It is the constituent on the crust of bread 
and in toast that is slightly sweet and becomes sticky when 
moistened with water. It is prepared in large quantities 
from starch for use as a mucilage, as on the backs of 
stamps and envelopes. 

Glycogen is sometimes called animal starch, since it is 
very similar to starch and is found in the liver and muscles 
of higher animals, and in clams and oysters. It is the 
only form in which reserve carbohydrates are stored in 
animals. During starvation the liver decreases greatly 
in size, due to the withdrawal and consumption of the 
glycogen for fuel. 

Cellulose constitutes the skeleton material of plants. 
All cell walls are made of it. In some plant tissues, as 
in woody stems and tree trunks, the cellulose walls are 
so thick and heavy that the whole tissue is hard and rigid. 
An especially compact and hard form of cellulose is that of 
nut shells and fruit stones. In the cotton plant long, fine 
threads of cellulose form a ball about the seeds. These 
threads constitute the cotton of commerce. In the flax 
plant, the vascular bundles of the stems when freed from 
the softer tissue around them, can be worked and spun 
into fine, hard, glossy threads. These are the linen of 
commerce. Paper, hemp, and jute are other cellulose 
products (Fig. 55). 

Relation of the Carbohydrates to Each Other. — Probably 
some of the most important chemical characteristics of the 
carbohydrates are the ways in which they are converted 



212 



THE PLANT BODY 





I i'. 55. Wool, cotton, flax, and silk fibers as they appear under the microscope. All our 
textiles are plan! products directly or indirectly, since the animals eat plants. Cotton and 
linen (flax) iir( ' composed of carbohydrates (cellulose) while wool and silk are composed of 
protein It is of ten possible to tell the composition of a cloth by microscopic examination of 
the threads, and by chemical tests for protein and cellulose. (From Bui. 15, Minn. Station.) 



RELATION OF THE CARBOHYDRATES TO EACH OTHER 213 

into one another. Excluding the pentoses from the dis- 
cussion, we may say that the hexoses are the simplest 
forms of carbohydrates ; they cannot be decomposed into 
simpler ones, and they cannot be converted into each other 
by simple chemical means. However, the dihexoses, as the 
name indicates, are composed of two hexoses in combina- 
tion. How can a dihexose be decomposed into hexoses f 
One of the simplest ways is by the action of the digestive 
juices. When we eat sucrose, the pancreatic juice, by 
means of one of its enzymes or ferments (see Chapter 
XVII) converts it into levulose and dextrose, thus: 



CjoHooOn 


+ 


H,0 


= C 6 H 12 6 


+ C c H 12 6 


sucrose 






levulose 


dextrose 



We do not know what the enzymes are chemically ; all we 
know is what they do. In this case the enzyme causes a 
molecule of water to combine with a molecule of sucrose, 
with the result that it is split into two molecules of hexose. 
Lactose is decomposed as follows : 



lactose 


+ 


H 2 = 


= C 6 H 12 O rt + C^Oe 
galactose dextrose 


e thus : 








C 12 H 2: Ai 
maltose 


+ 


H 2 - 


= C (i H 12 0, ; + C 6 H :2 6 
dextrose dextrose 



This process of combining ivith water is called hydrolysis. 
All of these disaccharides are hydrolyzed by the digestive 
juices before being absorbed into the blood stream. 

Starch is hydrolyzed first into dextrin, then into mal- 
tose, then into dextrose. The following equations repre- 
sent the important steps in the process : 



2C 6 H 10 O 5 + 
starch 



HoO = 



c ie o 22 o 11 

maltose 



CkjH^Oh 

maltose 



HoO 



C 6 H 12 6 + CeH^O. 
dextrose dextrose 



214 THE PLANT BODY 

Or, these two equations can be combined into one by 
assuming that one molecule of C 6 H 10 O 5 takes up one mole- 
cule of water and becomes dextrose. Glycogen is hydro- 
lyzed in the same way as starch. Certain forms of 
cellulose can be partially digested by animals but not by 
humans. Cellulose constitutes the bulk of the indigestible 
matter of foods. 

Hydrolysis of carbohydrates can be brought about by 
agents other than enzymes. The most important of these 
are acids. By boiling any of the disaccharides with a 
little dilute acid, especially hydrochloric, they are hydro • 
lyzed into their corresponding hexoses. Starch, glycogen, 
and dextrin can likewise be hydrolyzed. Corn syrup con- 
sists principally of dextrose and maltose, produced by 
the hydrolysis of cornstarch by means of acid. Strong 
sulfuric acid will attack even cellulose in such a way that 
it can be hydrolyzed to dextrose. 

2. Fats. — The fats, like the carbohydrates, are com- 
pounds of carbon, hydrogen, and oxygen. But, unlike the 
carbohydrates, they do not contain two atoms of hydrogen 
for every one of oxygen. In fact, the percentage of the 
three elements in these two classes of compounds is very 
different, as is shown in the following table: 



Per cent 
of C 



Per cent 
of H 



Per cent 
of O 



Carbohydrate (starch) 
P^at (stearin) 



40 

77 



7 
)-2 



53 

11 



Thus, there is far more carbon and hydrogen in fats; 
and since these are the two combustible elements, the fuel 
value of fats is greater than that of carbohydrates. One 
pound of fat is equivalent to 2.4 pounds of starch in its 
fuel value. 



DECOMPOSITION OF FATS 215 

Plant and Animal Oils and Mineral Oils. — This group of 
compounds is often spoken of as fats and oils. What is 
the difference between a fat and an oil? Simply that 
the former is a solid, and the latter a liquid, at ordinary 
temperature. In our discussion here, we are excluding the 
so-called mineral oils. They are products of petroleum 
and are composed of but carbon and hydrogen, whereas 
fats are of plant or animal origin and are composed of 
carbon, hydrogen, and oxygen. 

Constitution of Fats. — Each fat molecule is composed of 
a molecule of glycerin united to three molecules of fatty 
acids (so called because they occur in fats). Thus stearin, 
the principal fat of beef suet, can be represented 
as follows: 

/C18H35O2 

CsHs^— — C18H35O2 

\Ci8H35O2 
glycerin 3 stearic acid molecules 

For this reason fats are called glycerides. Fats from 
different animals and plants differ from each other be- 
cause of different fatty acids contained in them. Thus in 
butter-fat one of the principal glycerides is palmitin, 
containing palmitic acid, C 16 H 32 2 ; in olive oil it is olein, 
containing oleic acid, C 18 H 34 2 ; in linseed oil it is linoleic 
acid, C 18 H 32 2 . Since a large number of acids are known 
to occur in fats, it is obvious that a great variety of fats 
and oils is possible. 

Decomposition of Fats. — Fats are hydrolyzed by intes- 
tinal enzymes, liberating the glycerin and the fatty acids. 
Also, they are decomposed by boiling alkali : 

CaH^CMH^Oa), + 3NaOH = C 3 H 5 (OH) 3 + 3 NaC 18 H 35 2 
stearin sodium glycerin sodium stearate 

hydroxide ( soap ) 

This is the process of soap-making , and is essentially the 
same for all soaps. It is seen that both glycerin and soap 



216 



THE PLANT BODY 



are formed (Fig. 56). This constitutes almost the sole 
source of the glycerin of commerce, which is very exten- 
sively used in explosives and in cosmetics. Soap can be 
defined as the sodium salt of a fatty acid. The soap will 
differ, of course, with the kind of acid present in the fat. 




V\(, 56. — The surface of soap kettle. These kettles are several stones deep, and make 

1,000 pounds of soap at a time. Fats, oils, and refuse grease of all kinds are boiled with 

alkali in the tub, until the fat is completely changed into soap. Salt is added to the resultant 

mixture, which causes the soap to rise and form a cake on the surface. 

Vov this reason soft fats and oils will not make firm, hard 
soaps. When wood ashes, containing potassium carbon- 
ate, are used for soap-making, as they were by our grand- 
mothers, the potassium salts of the fatty acids result and 
these are all "soft soaps." 

Uses for Fats and Oils.— Probably the most important 



PLANT ACIDS 217 

use of these substances is as food, because of their high 
value in furnishing energy to the body. Another use to 
which enormous quantities of the cheaper fats are put is 
in the manufacture of soap, described above. Soap is 
probably the best of all cleaning agents ; and it has been 
said that the degree of civilization of a people can be 
measured by the amount of soap that it uses. Linseed oil 
(from the seed of the flax plant), and a few others of less 
importance, have the property of combining with oxygen 
when spread out in a thin layer and of forming a hard, 
resistant film. It thus forms the basis for practically 
all paints. Some oils, such as that of the castor bean, have 
medicinal uses. 

One of the greatest triumphs of industrial chemistry 
was the discovery of a way of converting vegetable oils, 
such as cottonseed oil, into a hard fat. The principal fatty 
acid in these oils is oleic, C 18 H 34 2 ; while that of the 
hard fat is stearic acid, € 18 H 36 2 . In other words, they 
differ by two atoms of hydrogen. When a method called 
hydrogenation was found for causing gaseous hydrogen 
to unite with the oil, a solid, white fat could be made ; such 
fats constitute practically all of our lard substitutes, and 
to a certain extent are used in margarines. 

3. Plant Acids. — The sourness of fruits and other parts 
of plants is due to certain organic acids, compounds of 
carbon, hydrogen, and oxygen. The acidity of lemons, 
oranges, and grape fruit is due to citric acid, C 6 H 8 7 . 
Malic acid, C 4 H 6 5 , is abundant in green apples; the 
' ' sugar sand ' ' that forms during the boiling of maple sap 
is calcium malate. Oxalic acid, C 2 H 2 4 , occurs in rhubarb 
stems and in sorrel. Tartaric acid, C 4 H 6 6 , is obtained 
from grape juice. Potassium hydrogen tartrate, KHC 4 - 
H 4 6 , is cream of tartar, a common component of baking 
powder. Lactic acid, C 3 H 6 3 , is formed during the fer- 
mentation of silage, and during the souring of milk. 



218 THE PLANT BODY 

Acetic acid, C 2 H 4 2 , is also a product of sila t fermenta- 
tion: it is the acid of vinegar. Tannic acid, or tannin, is 
the substance used in tanning leather. It is found in 
many plants bu1 is especially abundant in oak bark, oak 
galls, and hemlock bark. The bitter, puckering substance 
oi strong tea is tannin. 

4. Volatile Oils. — Under this heading will be grouped 
all those substances which give plants their characteristic 
odors and flavors. Most of them are compounds of car- 
bon, hydrogen, and oxygen, although a few contain sulfur. 
The delightful odors and flavors of fruits, the delicate 
perfumes of flowers, the pungent aroma of pine needles, 
the permeating odor of garlic, mustard, and cabbage, the 
irritating fumes of onions, all belong to this group. Some 
others of great commercial importance are turpentine 
and camphor. 

5. Coloring Matter. — The most important, of course, is 
the green chlorophyll, for this is the substance which 
brings about the photosynthesis of carbohydrates, as we 
have seen before. The coloring matter of some plants, as 
the indigo, the logwood, the madder, is of commercial 
importance as dyes. 

6. Proteins. — These compounds are composed of the 
elements carbon, hydrogen, oxygen, nitrogen, and sulfur, 
the nitrogen being an especially characteristic element. 
The living protoplasm of the cells of all animal and plant 
tissues is composed largely of proteins. Hence, we must 
consider them as being of the very greatest importance in 
the plant and animal bodies. Muscle and nerve tissue are 
almost wholly protein; the white of egg is a familiar pro- 
tein that is soluble in water. The casein of milk, which 
forms the curd in sour milk and in cheese-making, is a 
protein of animal origin that contains calcium and phos- 
phorus besides the above-named five elements. The glu- 
ten of wheat, a mixture of two proteins, is one of the most 



GERMINATION OF THE SEED 219 

easily prepared plant proteins. By enclosing a cup of 
flour in a muslin bag, and carefully kneading it under 
water, a gummy, rubbery, elastic mass remains ; this is the 
gluten to which is due the great rising capacity of wheat 
bread. Similar glutens can be prepared from rye, oats, 
and barley, but they are far less elastic than that of the 
wheat, which explains the fact that wheat flour is the only 
kind that will make a well-risen, light, porous loaf of 
bread. Gelatin is another well-known protein obtained 
from the bones and sinews of packing-house animals. It 
has a remarkable capacity for absorbing water. Even a 
three per cent solution of it in water is a firm jell. Gela- 
tin is unique among the proteins in that it contains but a 
trace of sulfur. All seeds contain a relatively large pro- 
portion of protein, as will be brought out in the chapter 
on feeds. 

7. Amides, — The amides and amino acids are rather 
simple nitrogenous compounds, found rather abundantly 
in leaves, seedlings, and other rapidly growing parts of 
plants. They are the simple building stones out of which 
the more complex proteins are constructed. They are 
important feed constituents, since a considerable portion 
of the nitrogen of hays is in these forms. 

8. The alkaloids are compounds that are characterized 
by unusual and powerful activities towards the various 
organs of the })ody. Some of the better known of these 
compounds are the nicotine of tobacco ; strychnine of 
strychnos wood; cocaine of the cocoa tree ; caffeineof coffee 
and tea; morphine of the poppy; and quinine of cinchona 
bark. Alkaloids are not found in all plants ; and when 
present are only in small amounts. They are nevertheless 
very important drugs and many plants are cultivated for 
their alkaloids alone. 

Germination cf the Seed. — There are two principal parts 
to a seed: (1 ) The embryo, or germ, which is a miniature 



220 



THE PLANT BODY 



plant, ready to grow and develop into the roots and leaves 
of the new plant; and (2) the endosperm, which is a store- 
house of food materials, especially starch, fat, and pro- 
tein, to nourish the new plant until it can get its own 
sustenance from the soil and air (Fig. 57). During the 




Fig. 57. — An experiment on bean seeds. The upper figures show three beans partly muti- 
lated. The one on the left was left whole; the middle one had half of the storage organs or 
cotyledons removed; the other had almost the whole of the cotyledons removed. In each 
case the embryo, or young plant, was uninjured. The lower figures show the three plants 
grown from these beans. It will be noticed that although each produced a plant, the larger 
and more vigorous plants came from the beans having the larger amount of storage organs 
present. This experiment shows the purpose of the two main organs of a seed, the embryo 
and endosperm. The embryo is a minute, dormant plant; when given moisture and food, 
it develops into the roots and leaves of the new plant. The endosperm is purely a storage 
organ; it does not grow, but furnishes sugar, nitrogen compounds, and minerals to the 

growing embryo. 

development of a new plant from the seed, several differ- 
ent stages in the process are observed: (1) The swelling 
of the seed by the absorption of water; (2) the develop- 
ment of roots : (3) the emergence of the primary leaves or 



CHEMISTRY OF GERMINATION 221 

cotyledons above ground; (4) the formation of the real 
or permanent leaves; (5) the shrivelling and drying up 
of the remains of the seed. 

Chemistry of Germination. — We are now in a position to 
discuss these phenomena from the viewpoint of the chemi- 
cal changes involved. The absorption of water before any 
start toward germination can be made is necessary for 
two very fundamental reasons: (1) There must be an 
abundance of water in the tissues for the transfer of food 
materials from the seed to the growing parts of the new 




Fig. 58. — Testing seeds for germination. Not all seeds have the power of absorbing water 

and then carrying on that series of chemical changes which we call sprouting. By wrapping 

samples of each lot of seeds in a wet blanket, or by placing them in a box on wet sawdust, 

the percentage of germination can be learned. 

plant (Fig. 58) ; and (2) before the protein, starch, and 
fat, which are insoluble in water, can be transferred to the 
growing parts, they must undergo hydrolysis to water- 
soluble compounds, and this process of hydrolysis of 
course requires water. These seed materials first absorb 
water, just as a sponge does, swelling up and bursting 
the seed coat. Then by means of enzymes, or ferments, 
contained in the seed, the proteins are hydrolyzed to 
amides and amino acids, the starch is hydrolyzed to mal- 
tose, and the fats to glycerin and soaps ; and the amides, 
maltose, glycerin, and soaps being soluble in water, can be 
carried to the growing parts, where they are used to build 



222 THE PLANT BODY 

up the n ssne. These processes of hydrolysis are not 

completed all at once; they are performed gradually, as 
s1 aa the growing plant requires the materials. 

The pushing down of new roots into the soil takes place 
very rapidly for a few days, because the water which the 
seed is able to absorb is far too scanty to supply the 
rapidly increasing demands of the new leaves, and more 
water must be obtained from the soil. Then, too, seeds are 
not very plentifully stocked with minerals, and a supply 
from the soil must be forthcoming as soon as possible. 

The cotyledons, or primary leaves, are usually a part 
of the embryo in the seed. They are rather fleshy, and 
well stocked with food material, especially in peas and 
beans. For this reason they can quickly make their way 
up through the soil and into the air. Then they become 
green in color; and from that time on they are able to 
manufacture their own carbohydrates from the carbon 
dioxide of the air. 

Very soon after this the true leaves begin to appear, 
and before long the new plant is able, by means of the 
leaves and the new root system, to obtain all its necessary 
food materials from the soil and the air. AYhen this state 
of development is attained, the mother seed is no longer 
needed and it soon shrivels up and ceases to function. 

QUESTIONS 

1. What reasons have we for helieving that plants appeared on earth 

before animal? ? 
■1. What products do we obtain from the earth to-day that had their origin 

in plant materials in by-gone a^r- 
•i. What are our leading products that are manufactured from plant 

mater ial- 1 

4. What i- the fundamental business of agriculture 1 Why? 

5. Make a brief outline of the ways in which chemistry applies to agri- 

culturc and to our daily life. 

6. What an- the raw material- out of which plants build up their tissues? 

mpute the amount of water transpired from an acre of alfalfa, as- 
suming 3 tone <>f the green crop per acre, and that 30 per cent, of this is 
'lry rnatr.-r. 

ire the purposei of this transpiration? 



LABORATORY EXPERIMENTS 223 

9. Explain why land is sometimes left fallow in order to conserve 
moisture. 

10. Write an equation showing the formation of starch from carbon dioxide 

and water. 

11. Name the conditions necessary to make photosynthesis possible. 

12. Make an outline of the carbohydrates, giving the formula of each, where 

found and their principal uses. 

13. Give a definition for carbohydrates. 

14. Outline the process of making granulated sugar. 

15. Write equations showing the hydrolysis of starch, maltose, and sucrose, 

naming all substances formed. 

16. Why do fats have a higher fuel value per pound than carbohydrates? 

17. Explain briefly the chemistry of soap-making. What is a soap, 

chemically ? 

18. What is meant by the hydrogenation of an oil ? How does it improve the 

oil for some purposes? 

19. Name four common plant acids and state where each is found. 

20. Of what chemical elements are proteins composed? Why cannot starch 

be used by the animal to build up muscle tissue ? 

21. Name three common protein substances. 

22. Name four common alkaloids, and state from what plant each is obtained. 

23. Write at least one page on the chemistry of a germinating seed. 

LABORATORY EXPERIMENTS 

65. To Study the Chemical Properties of Sugars. — (a) Heat 10 c.c. 
of mixed Fehling's solution * to boiling, add a few c.c. of dilute dextrose 
solution or diluted corn syrup (containing dextrose and maltose) and boil. 
The red precipitate is copper oxide, CuqO, and is formed by the action of the 
sugar on the copper compound of Fehling's solution. 

(b) Repeat, using a solution of levulose, or diluted honey (containing 
levulose and dextrose). 

(c) Repeat, using cane sugar (sucrose). If a negative test is obtained, 
boil 5 c.c. of a dilute sucrose solution with one drop of dilute hydrochloric 
acid for a few minutes, neutralize the acid with sodium hydroxide solution, 
and then, test with Fehling's solution. What change toqj: place in the 
sucrose? What is the cause of this change? 

(d) Repeat, using maltose. 

(e) Repeat, using lactose. 

(f) What sugars give positive tests with Fehling's solution? How 
would you test for the sugar in a sugar beet ? 

66. To Study the Chemical Properties of Starch. — (a) Dissolve about 
0.1 g. of starch in 20 c.c. of water by boiling. Cool, and add a drop of 
iodine solution t to a portion of it in another test tube. Repeat the test 
on the starch solution diluted with 4 volumes of water, then with 10 volumes 
of water. 

* Fehling's solution is made up in two parts as follows : Part A con- 
sists of 34.6 g. of copper sulfate dissolved in 500 c.c. of water. Part B con- 
sists of 173 g. of Rochelle salt (sodium potassium tartrate) and 50 g. of 
sodium hydroxide dissolved in 500 c.c. of water. Just before using, equal 
volumes of A and B are mixed. 

t Dissolve 0.4 g. iodine and 1.5 g. potassium iodide in 100 c.c. water. 



224 THE PLANT BODY 

(b) Test the starch solution with Failing's Bolution. 

(c) Repeat (a) and (b> after boiling the starch solution with a drop 
• f dilute hydrochloric acid. Explain the latter change. 

67. To Show the Presence of Sugars and of Starch in Various Plant 
Materials. — (a) Chop up small pieces of various vegetables and fruit- 
squeeze out the juices 1 . boil them in a little water for a few moments, then 
test with Folding's solution and. after cooling, with iodine solution. Make 
a table of the results, using + to indicate a positive test and — for a 
negative test. 

(b) Put a drop of iodine solution on slices of raw and of cooked vege- 
tables. Which gives a better iodine test, raw or cooked starch ! 

(c) Dilute some maple syrup with 10 times its bulk of water. Hydrolyze 
10 c.c. of it as was done in experiment 65 (ci, then test with Fehling's 
solution. Test another 10 c.c. portion without hydrolyzing. What it appa- 
rently the principal sugar in maple syrup? 

(di Repeat the process outlined in (o on the extract of some slices of 
sugar beet. What sugar is most abundant here? 

68. To Study the Properties of Fat. — (a) Smear a little cottonseed or 
other oil on a piece of filter paper and hold towards the light. Result? 

(b) Place a few drops of oil in the bottom of each of 5 test tubes. 
Test the solubility of the oil in water, wood alcohol., turpentine, gasoline, 
and carbon tetrachloride. The latter is the safest fat solvent to use in a lab- 
oratory because it is non-inflammable. 

(c) Place a few drop- of oil in each of four test tubes. Add to the 
tubes the following: water, soap solution, 1 per cent hydrochloric acid, 
and 1 per cent sodium hydroxide solution. Place the thumb over the 
mouth of each tube and shake violently. In which cases does the oil remain 
in a milky suspension for some minutes? These suspensions are called 
emulsions. They are not true solutions of the fats as were obtained in (bi. 
From this experiment, what two solutions would be best for washing greasy 
clothes and dishes? Which of these two do we use and why? 

69. To Make Soap. — Place 10 or 15 g. of lard, tallow, or cottonseed or 
other oil in a beaker, add 100 c.c. of 10 per cent sodium hydroxide solution 
and boil gently. At intervals drop a few c.c. of the mixture into water. 
When it dissolves completely, without showing any drops of oil still un- 
changed, remove from the flame. The beaker now contains a mixture of 
soap, glycerin, water, and a little excess sodium hydroxide. Dissolve about 
25 g. of sodium chloride in it, and allow to cool. The brine causes the soap 
to rise to the surface, where it hardens and can be removed in a cake. Ex- 
amine to see how it compares with commercial soap. Dissolve it in warm 
water, then add dilute hydrochloric acid until the solution is distinctly 
acid. According to the following equations, what is the substance that 
rises to the top? 

<■}].<( \H. -<),)., + 3XaOH = C,H 6 (OH), + 3 XaCJ^a 
stearin glycerin -odium 

(fat) stearate 



(soap 



NaCVH r ,0,, + HC1 = HCVH^A + XaCl 
-odium stearate stearic acid 

Wlint becomes of the glycerin in the manufacture of soap? 



LABORATORY EXPERIMENTS 225 

70. To Show the Cause of the Drying of Linseed Oil.— Place a thin 
layer of linseed oil over the bottoms of two small bottles. Fill one bottle 
with CO, (see experiment 21 ) and stopper it tightly. Stopper the other bottle 
full of air, and let them stand for several days. Then examine them to 
see in which bottle the oil has dried. What constituent of the air causes 
the drying? How else could the drying have been prevented? 

71. To Show the Reaction of Plant Juices.— With both blue and red 
litmus paper test the reaction of the juices of various fruits, vegetables, 
silage, etc. 

72. To Study the Properties of Tannin.— Make a dilute solution of 
tannin. Add a drop of dilute iron sulfate or iron chloride solution to it. 
Add some of the iron solution to a strong extract of green tea. What com- 
mercial use is made of this reaction? 

73. To Prepare Wheat Gluten. — Make a stiff dough out of about 25 
g. of flour, let stand under water for 30 minutes, place in a muslin bag or 
cloth, and wash under running water until the starch is all removed. The 
residue is wheat gluten. Describe it. What property does wheat gluten 
possess which enables wheat flour to form a lighter loaf of bread than any 
other kind of flour? Prove the presence of nitrogen in it as was done in 
experiment 60. Test with concentrated nitric acid (see experiment 44). 
To what class of substances does gluten belong? 

74. To Show the Hydrolysis of Starch Into Maltose.— Soak about 30 
barley or other seeds in water for several hours, then plant in moist sand 
or sawdust in a box. When the sprouts are about an inch long, remove 
the seedlings, wash away the sand and sawdust, grind them in a mortar 
with about 25 c.c. of water and filter. Grind 30 unsprouted seeds in the 
same amount of water and filter. Test 5 c.c. portions of the two filtrates 
for sugar with Fehling's solution. Explain the results. 

75. To Show the Presence of Fat in Seed. — (a) Place 20 g. of corn- 
meal in a bottle with 50 c.c. of gasoline or preferably carbon tetrachloride, 
and shake occasionally for an hour. Filter and evaporate some of the 
filtrate to dryness on a watch glass. Rub some of the residue on filter 
paper. Carefully heat some of it. Do these tests indicate what the sub- 
stance is? 

(b) Place the germ of a corn kernel in a piece of filter paper and mash 
it with a hammer. Explain the results.. 



15 



CHAPTER XVI 

THE ANIMAL BODY 

Plants the Only Feed for Animals. — Plants constitute 
almost the sole feed for animals, especially farm animals. 
If when animal tissue is eaten by other animals, we con- 
sider that this tissue was in turn produced by the eating 
of plants, it is readily seen that plants are ultimately the 
sole support of animal life. The fundamental chemistry 
behind this natural arrangement is simply this : The feed 
of animals consists principally of carbohydrates, fats, and 
proteins. The mineral world, the soil, the waters of the 
earth, do not contain such compounds, except in extremely 
small amounts. The carbon for these compounds must 
all come from the carbon dioxide of the air. Plants can 
feed on this source of carbon, but animals cannot. There- 
fore, the plants must make these compounds and then the 
animals must eat the plants. 

We must look upon the compounds in the plant body 
as the raw materials from which the animal constructs its 
various tissues. Let us examine, then, the same series of 
compounds that we studied in the last chapter, just as 
regards their occurrence and use in the animal body. 

Water. — As in plants, water is the most abundant con- 
stituent in animals. It comprises from 45 to 65 per cent 
of the body in most animals; in a fat hog it is only about 
4_! per cent. As the animal puts on fat, the percentage of 
water, of course, decreases. Water is not very abundant 
in the bones, and in the fatty tissues of hogs is as low as 
7 per cent. Water plays an important part in digestion, 
which will be discussed later. 
226 



FATS 227 

Mineral Matter. — The animal body consists of from 
1.5 to 5.0 per cent of mineral matter, mostly located in 
the bones. It is thus not as abundant a constituent as it 
is in the plant body. Necessarily, the elements present in 
the ash of animals are the same as those in the ash of 
plants, since the only source of these elements is the plants 
that are eaten. However, the animal selects certain ele- 
ments and stores them in proportionately larger amounts 
than are found in the plants. For example, the animal 
requires calcium and phosphorus for the bones, and chlo- 
rine for the hydrochloric acid of the stomach; hence it 
must eat plant material plentifully supplied with them. 
On the other hand, the animal needs no silicon, which is so 
abundant in plants, and hence this element is practically 
all excreted. 

Carbohydrates. — As was mentioned under this heading 
in the preceding chapter, the only two carbohydrates that 
are actually built up by the animal are the lactose of the 
milk and the glycogen of the liver and muscle tissue. The 
former, of course, furnishes feed for the young, while 
the latter constitutes a reserve supply of carbohydrates 
in the animal body. The animal forms these carbohy- 
drates out of the various plant carbohydrates in its food. 

Fats. — Animal fats represent a great variety of forms, 
from the thin oils of fishes to the hard tallow of beef and 
mutton. Their fundamental composition of glycerin and 
fatty acids is the same as that of the plant fats, their dif- 
ferent characters being due to the different kinds of fatty 
acids. In the animals there are special kinds of fat-like 
substances containing phosphorus that are found espe- 
cially in brain and nerve tissues. There are also protein- 
like phosphorus compounds that are characteristic of the 
liver, pancreas, and thymus gland (sweetbread) . For this 
reason these organs are often recommended as food for 
children suffering with disorders of the nervous system. 



228 THE ANIMAL BODY 

The fats, in animals as well as in plants, are a reserve of 
nourishment in a concentrated form. They also serve as a 
protection against cold, as they are usually abundant just 
beneath the skin. The animal can convert the plant fats 
into its own particular kind of fat to a considerable degree. 
It can also convert carbohydrates into fat ; hence the ad- 
vice to fat people to avoid eating much sugary foods. 

Plant Acids. — The acids that are so characteristic of 
plant juices do not have their counterparts in the animal. 
When these acids are eaten by animals they are usually 
assimilated the same as other food compounds, or are 
excreted in the urine in the form of salts. The only acidic 
fluid of the animal body is the gastric juice of the stomach ; 
and the acidity here is due to hydrochloric acid. At times 
the urine may be slightly acid, due to various mineral 
compounds, but not to acids containing carbon. 

Volatile Oils. — These do not have their counterparts 
in the animal world. 

Coloring Matter. — The most prominent colored sub- 
stance of the higher animals is the red blood corpuscles, 
and one of the remarkable facts in the chemistry of plant 
and animal life is that the green chlorophyll of plants 
and the colored constituent of the blood corpuscles are the 
same substance, except that the plant pigment contains 
magnesium where the animal contains iron. The functions 
of the two are also similar; the blood corpuscles supply 
the body with energy by carrying oxygen from the lungs 
to the various tissues, where it oxidizes the food to pro- 
duce energy; and the chlorophyll in plants absorbs the 
energy of sunlight and enables the plant to use it in the 
manufacture of starch. Other animal pigments, such as 
those of the skin, feathers, fur, and bile are not related, 
so far as is known, to plant pigments ; and the animal does 
not use the plant pigments as raw materials for construct- 
ing its own pigments. 



GENERAL COMPOSITION OF THE ANIMAL BODY 



229 



Proteins. — The muscle tissue, the hair, skin, nails, ten- 
dons, and connective tissues, also most of the material 
of nerve tissues, consist of proteins. The casein of milk 
is another familiar animal protein. Gelatin is a protein 
obtained from bones. To build up these proteins the 
animal must eat plant proteins. In the process of diges- 
tion, as we shall see later, the proteins of the feed are 
broken down into the simple amino acid units of which 
they are composed ; these are carried by the blood to the 
various tissues and are there rebuilt into the particular 
kinds of protein that are wanted. 

Amides and amino acids are not found in animals except 
in the digestive tract and in very small amounts in the 
blood, where they occur only temporarily before being 
built up into proteins. 

Alkaloids. — These are not found in any animal. If they 
are taken as medicine or are eaten in plants, they are elimi- 
nated through the kidneys in a short time. 

General Composition of the Animal Body. — The accom- 
panying table shows the composition of various farm 

Table XVII 

Composition of Farm Animals 

Content of 

intestinal 

tract 



Fat steer 

Half -fat steer 
Lean sheep . . 
Fat sheep . . . . 
Half -fat pig . . 
Fat pig 



Water 


Fat 


Protein 


Ash 


Per cent 


Per cent 


Per cent 


Per cent 


45 


30 


15 


4 


51 


19 


17 


5 


57 


19 


15 


3 


43 


36 


12 


3 


55 


23 


14 


3 


41 


42 


11 


2 



Per cent 

6 
8 
6 
6 
5 
4 



animals, exclusive of the contents of the stomach and 
intestines. It serves as a concrete summary of the pre- 
ceding paragraphs. The data are from the Rothamsted 
Experiment Station in England. It will be noticed that 



230 THE ANIMAL BODY 

the protein and ash content are rather constant for one 
kind of animal, but that the fat and water content vary 
in opposite directions according to the condition of the 
animal. The fat pig- contains the least ash, protein, and 
water, and the most fat, of all farm animals. The carcass 
of the hog also produces the greatest proportion of 
dressed meat. 

QUESTIONS 

1. What i> the fundamental chemical reason why animals are entirely de- 

pendent on plants for their feed? 

2. Make a list of all the classes of compounds found in plants, and state 

specifically what the animal does with each when it is taken into 
the body. 

3. How does plant ash differ from animal ash in composition? 

4. How does chlorophyll differ from the hemoglobin of the blood corpuscles? 

What purpose does each serve? 

5. Name 5 animal proteins. 

t>. Xame several animal fats and give the use of each. 

LABORATORY EXPERIMENTS 

76. To Test for Sugar in Various Animal Tissues. — Repeat experi 
meat H7. using various animal tissues, siich as ground bone, muscle, liver. 
hair, etc.. in testing for sugar. Result-': 

77. To Test for Water in Animal Tissues. — Using the apparatus used 
in experiment 10. test several animal tissues. 

78. To Show the Presence of Fat in Lean Meat. — Using 20 g. of bepf 
from which every visible particle of fat has been removed, test for fat ac- 
cording to the directions in experiment 7o. Results? 



CHAPTER XVII 

THE NUTRITION OF THE ANIMAL BODY 

Function of Feed. — Chemical processes are going on 
continually in the animal body. Some of these consist in 
the generation of heat to keep the body warm and to fur- 
nish the energy for doing physical and mental work. 
Some of them consist in the actual doing of work by mus- 
cle and nerve fibers. Still other processes consist in the 
transfer of material from one part of the body to an- 
other; the building up of storage tissue for fat; the con- 
version of feed into forms which the blood can absorb; 
the increase in the number of cells in the various tissues, 
and hence in the size of the whole body; the formation of 
eggs and of young and the elimination of waste products. 
These various activities require raw materials with which 
the work can be done. These raw materials constitute the 
feed of the animal. 

In general we may say that there are four great classes 
of activities in the body: (1) The production of heat and 
energy; (2) the repair of tissue ; (3) the formation of new 
tissue, and (4) the maintenance of health. Feed must 
contain the necessary raw materials to meet all four of 
these requirements. Each of these will be dis- 
cussed separately. 

(1) The production of heat and energy is usually 
brought about by the burning of carbohydrates and fats, 
although proteins can also serve this purpose. The amount 
of energy produced in an animal body is directly propor- 
tional to the amount of work performed and to the amount 
of heat required to keep the body warm. Thus a horse at 
rest does not burn up as much fuel in a day as a horse at 

231 



232 THE NUTRITION OF THE ANIMAL BODY 

work. A bookkeeper requires only half as much fuel food 
a day as a lumber-jack or fireman. And a person living in 
a cold atmosphere requires more heat production in the 
body than a person in a warm atmosphere. 

Heat is usually measured in calories. Technically the 
calory is the amount of heat required to raise the tem- 
perature of one gram of water one degree Centigrade. 
The heating value of a substance is measured by burning 
it in an apparatus called a calorimeter. This instrument 
is used for both fuels and foods. We can most easily 
think of calories in the following terms : An average slice 
of bread (1.3 ounces) furnishes about 100 calories; a glass 
of milk, 150 calories; a large potato, 150 calories; an 
egg 7 80 calories ; a cubic inch of butter, 160 calories ; one- 
fourth of a pound of lean meat, 250 calories (Fig. 59). 

The average man at desk work develops about 2200 
calories per day; a man at moderate physical work about 
2800 calories ; a farmer, 3500 calories. The large amount 
of fat eaten by Eskimos is explainable by the great amount 
of heat that must be developed in the body in order to 
maintain its normal temperature. 

(2) By the repair of tissue is usually meant the repair 
of muscle and nerve tissue, not fatty tissue ; for the former 
are the tissues that are used in performing work, and they 
wear out as a consequence of this w T ork done. Since these 
tissues are composed of protein substances, they require 
protein substances for making repairs, for the elements 
nitrogen and sulfur are lacking in the carbohydrates and 
fats. Then, too, the simple amino acids of which the pro- 
teins are composed, apparently cannot be formed by the 
animal body from simpler raw materials as the plants 
can. Therefore, the animal must take the plant proteins, 
decompose them in the process of digestion into the amino 
acids, and then recombine the latter in different propor- 
tions into the particular proteins of the animal body. For 



FUNCTION OF FOOD 



233 




Fig. 59. — One pint of milk — 337 calories -and its energy equivalent in other food materials. 

The weight for each food is given below: 

Food materials Weight (oz.) 

1. Skimmed milk 32 .4 

2. Whole milk 17 .2 

3. Cream 6.1 

4. Cabbage 45 .0 

5. Onions 27 .0 

6. Sugar 3.0 

7. Honey 3.6 

8. Potatoes 17.7 

9. Grapefruit 35.0 

10. Peanuts 2.9 

11. Apples 25 .3 

12. Bananas 18 .7 



13. 
14 


Food materials 
English walnuts 


Weight (oz.) 

6.3 

4.6 


15. 
16 


Shredded wheat 


3.3 

4.6 


17 




3.0 


18 




3.4 


10 




2.7 


an 




1 .9 


°i 




6.2 


99 




9.0 


?3 




1.6 


24 


Cheese 


2.7 



(From Farmers' Library Bui. 63, Minn. Agric. Exp. Station.) 



23 1 III I : NUTRITION OF THE ANIMAL BODY 

this reason all proteins are not of equal value as food, 
because of their scarcity in one or more of the amino acids ; 
tor the nutrition of man, some of the best proteins are 
those of milk, eggs, lean meat, and beans, especially soy ; 
the proteins of the cereal grains are of medium value ; and 
gelatin is very poor. 

Under the subject of the repair of broken-down tissue 
should be mentioned the repair of the bones and the re- 
plenishing of the mineral matter of the blood and of other 
(lu ids and tissues. There is a daily loss of calcium and 
phosphorus from the bones, of chlorine from the stomach 
juice, of iron, potassium, phosphorus, calcium, and mag- 
nesium from the blood. These losses must be made good 
by the minerals in the foods. Milk supplies an abundance 
of calcium, phosphorus, and potassium, but practically no 
iron ; vegetables, especially the leafy ones, and fruit con- 
tain considerable iron, calcium, magnesium, chlorine, 
and potassium. 

(3) THe formation of new tissues is a process almost 
identical with the process of the repair of tissue just dis- 
cussed. The growth of muscle and nerve tissues requires 
protein food; the growth of bone requires calcium and 
phosphorus ; the increase in volume of blood requires pro- 
teins and mineral materials. Under this heading should 
come those special cases of the formation of new tissues 
and fluids, as the production of milk, the laying of eggs, 
and the production of young. Since each of these three 
products either consists of a new animal body, or is the 
complete feed of a young animal, it is obvious that they 
must contain all the chemical elements found in the animal 
body, and that they contain proteins built up of the proper 
amino acids. Hence the great necessity for providing 
proper feed to milch cows, laying hens, and preg- 
nant animals. 

Vitamines. — There is another factor just recently dis- 



ENZYMES 235 

covered which enters into the question of the proper nutri- 
tion of growing animals. Substances called vitamines, of 
unknown chemical composition, are necessary in food for 
the promotion of growth and the maintenance of good 
health. There are at least three vitamines; the lack of 
any one of them is shown by the failure of an animal to 
grow, even though its food may be perfect in respect to 
protein, energy foods, and minerals. Milk, leafy vege- 
tables, roots, clover, alfalfa, grass, and raw fruits are 
rich in vitamines ; cereals and meat are poor in them. 

(4) The maintenance of good health is a rather vague 
phase of the function of foods, but in some particulars 
it is very important. What is meant by it here is the 
prevention by vitamines of the so-called nutritional dis- 
eases; beri-beri, common in the Orient from the almost 
exclusive use of polished rice for food ; scurvy, the disease 
prevalent among sailors and Arctic explorers, who eat 
practically no fresh vegetables, fruits, or milk ; and pos- 
sibly rickets, a common children's disease. The vitamines 
which prevent these ailments are abundant in milk, fruits, 
vegetables, and the germ of wheat and other seeds. 

To summarize the above discussion of the function of 
food, it may be said that there are four classes of food 
substances: (1) Fats and carbohydrates ; (2) proteins; (3) 
mineral elements ; and (4) the vitamines. 

Enzymes. — Profound chemical changes take place in 
food during the processes of digestion. The means by 
which these changes are brought about are exceedingly 
interesting. There are certain substances secreted by the 
walls and glands of the alimentary tract that have the 
power of inducing chemical changes to take place in the 
food materials. These substances are called enzymes. 
Their chemical nature is unknown ; we do not know their 
formulas, nor even the chemical elements of which they 
are composed. They are destroyed by boiling (compare 



236 THE NUTRITION OF THE ANIMAL BODY 

experiment 71), page 244). The enzymes are known by 
the work they do. Tims, the?'e are starch-hydrolyzing 
enzymes, protein-hydrolyzing enzymes, and so on through 
a long list of substances which are acted upon by enzymes. 
The saliva contains an enzyme called "ptyalin" which 
hydrolyzes starch into maltose; the "pepsin" of the stom- 
ach acts on proteins; the "lipase" of the pancreas con- 
verts fats into glycerin and fatty acids. 

Other living organisms secrete enzymes. Thus, when 
yeast grows in a solution of sucrose, it first secretes an 
enzyme which converts the sucrose into dextrose and levu- 
lose ; then it secretes another enzyme which converts these 
two sugars into alcohol and carbon dioxide. When seeds 
sprout, enzymes convert the starch into sugar; hence the 
sweetness of barley malt. The "rennet" of the cheese- 
maker is an enzyme prepared from calves' stomachs. 
Several dried preparations of enzymes are now in use 
in medicine. 

The Digestion of Food. — The nutrition of plants and 
the nutrition of animals are similar in at least one respect : 
the food of each of these classes of organisms must be in 
water solution. In plants it must be dissolved in the soil 
water before it can enter the roots. In animals it must be 
dissolved by the digestive juices before it can pass through 
the walls of the intestine into the blood stream. Food has 
not actually entered the tissues of an animal until it has 
arrived in the blood; for the digestive tract of an animal 
is simply a cavity running from end to end of the body, 
and food in this cavity is not really food in the body. 

Therefore, the primary object of digestion- is the 
changing of food info a form which is soluble in water. 
The insoluble food is acted upon by the various fluids along 
the digestive tract, each portion performing a different 
pari of the work. Digestion consists in chemical changes 
almost entirely. The changes are brought about by the 



DIGESTION IN THE STOMACH 237 

enzymes secreted by the walls of the alimentary canal and 
by the liver and pancreas. 

Digestion in the Mouth. — The first act in the taking of 
food into the body is chewing, or mastication. The object 
of this is to grind np the food into finer particles, and 
to mix them thoroughly with the saliva. The saliva con- 
tains an enzyme which converts starch into maltose : 

2C,,H 1I1 5 + ILO = C ]2 H 2; Ai 
starch maltose 

The sweet taste acquired by a piece of bread after 
a minute's chewing is due to the maltose formed. Pro- 
teins, fats, and carbohydrates other than starch are 
not affected by salivary digestion. The saliva is 
faintly alkaline. 

Digestion in the Stomach. — The stomach has a rather 
strong acid reaction, due to the hydrochloric acid secreted 
by the stomach walls. There are two enzymes in the gas- 
tric juice ; one is called rennin, or rennet, the other pepsin. 
The purpose of the rennin is to curdle the casein of milk, 
making a semi-solid out of the milk. This evidently is a 
provision of nature for making digestion easier. Rennet 
prepared from calves' and pigs' stomachs is used in 
cheese-making for producing the curd, and is also con- 
tained in "junket" tablets for making milk puddings. 
The pepsin is an enzyme which acts upon proteins. The 
action is one of hydrolysis (p. 213) as in the case of starch 
above, but the reaction is such a complicated one that it 
cannot be represented by an equation. The pepsin breaks 
down the proteins to simpler compounds, but not clear 
down to amino acids; that work is left for the enzymes 
found in the small intestine. The fats and carbohydrates 
are not acted upon in the stomach. 

In the ruminants or cud-chewing animals, the stomach 
is not a simple pouch, but consists of a series of four 



238 THE NUTRITION OF THE ANIMAL BODY 

pouches. The food after partial chewing is first stored 
in t he paunch. Here the saliva digestion continues, for the 
paunch does not secrete an acid juice, which would destroy 
the action of the saliva. From the paunch the animal re- 
turns the food to the mouth in the form of cuds, which are 
further reduced by chewing and then delivered to the 
other pouches. 

The muscles of the stomach walls maintain a slow- 
churning action which serves to mix the food very thor- 
oughly with the gastric juice. 

Digestion in the Intestines. — It is here that the greater 
part of the digestive processes takes place. The juices 
of this portion of the digestive tract are again slightly 
alkaline in reaction. They consist of juice secreted by the 
walls of the intestine, of bile secreted by the liver and 
poured into the intestine through a duct, and of pancreatic 
juice, secreted by the pancreas and furnished to the small 
intestine by the pancreatic duct. The intestinal juice con- 
tains an enzyme for hydrolyzing whatever starch was not 
changed by the saliva ; an enzyme for converting the mal- 
tose into dextrose ; enzymes for hydrolyzing sucrose and 
lactose into their respective simpler sugars (p. 213) ; and 
a protein-splitting enzyme called erepsin, which continues 
the work of the pepsin of the stomach and decomposes 
the proteins into simple amino acids. 

The pancreatic juice contains three enzymes : one for 
digesting protein, one for starch, and one for fats. The 
first two assist the corresponding enzymes of the intestinal 
juice. The fat-hydrolyzing enzyme is very important; by 
its action the fat molecules are split into glycerin and fatty 
acids. The latter combine with the sodium bicarbonate of 
the pancreatic juice to form soaps. Thus glycerin and 
soaps are the dii^cHtive products of fats. The fat enzyme 
is greatly assisted in its work by the bile. This contains 
substances which help to emulsify the fat; that is, to 



ASSIMILATION 



239 



break up the fat into very fine globules and to suspend 
these throughout the mass of digesting food. (Compare 
experiment 68.) In this condition the fat can be much 
more easily attacked by the fat enzyme. 

No enzymes have been prepared from the digestive 
tract that will dissolve cellulose. It is very probable that 
the bacteria which swarm in the intestine serve to digest 
a portion of the cellulose into the simple sugar dextrose. 

Assimilation.— From the above discussion it will be seen 






Fig. 60. — A herd of beef cattle. They are chemical factories for converting the proteins, 

fats, and carbohydrates of the pasture grass into the corresponding compounds of their 

bodies, for use as human food. 

that practically the sole object of digestion is to convert 
the insoluble foodstuffs into water-soluble forms. Thus 
the products of digestion are dextrose, levulose, galactose, 
amino acids, glycerin, and soaps, all of which are dissolved 
in the water of the intestinal contents. As fast as they 
are formed they are absorbed through the walls of the 
intestine and pass into the blood system. In this they are 
carried to all parts of the body, to be built up into this or 
that tissue or organ, or burned up for fuel, or stored for 
future use. The material which will not dissolve passes 
on down the intestinal tract and then out of the body. 



240 THE NUTRITION OF THE ANIMAL BODY 

In building up muscle or nerve tissue, the building 
stones are the amino acids from the digested proteins. 
The body selects the kinds and quantities of these building 
stones that are required for making a certain kind of 
protein tissue. Thus it is possible for us to eat egg pro- 
tein, and convert it into muscle fiber ; if any amino acids 
are left unused, they are burned up as fuel. The hen can 
eat the protein of grains and of meat scraps and convert 
t hem into egg protein. And a hog can eat the great variety 
of protein found in city garbage and convert it into pork 
(Figs. 60 and 61). 

In building up bony tissue, the animal selects the cal- 
cium and phosphorus from its feed, no matter what the 
compounds of these two elements are in the feed, and 
combines them into calcium phosphate. 

In storing up fat in fatty tissue, the animal must take 
the glycerin from the digested fats, together with those 
fatty acids now in the form of soaps, which are required 
to form the particular kind of fat found in that animal. 
Thus both a cow and a sheep may eat silage and clover 
hay; the sheep will convert the fat of these feeds into 
mutton-tallow, while the cow will convert them into butter- 
fat. Any fatty acids which are not used in this way are 
burned up for fuel. It has been found that a cow in 
manufacturing such large amounts of butter- fat every 
day must vary the selection of fatty acids to a certain 
degree, depending upon the kinds that are furnished in 
the feeds. Thus a cow eating considerable linseed 
meal will produce a softer fat than one eating grains which 
contain harder fats. 

Elimination of Waste.— Just as in the burning of fuel in 
a stove there is waste, so also is there in the burning of 
fuel and in the performance of work in the body. And 
just as in the stove there are the ashes which are not 
combustible, and the gaseous products of combustion 



ELIMINATION OF WASTE 



241 



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p-p g. 
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242 THE NUTRITION OF THE ANIMAL BODY 

which pass up the chimney, so also are there two kinds of 
waste in the body. Xot all of the food is digestible, hence 
there is a certain residue always left in the intestines 
which resists the action of the intestinal enzymes. This 
passes out of the intestines as the faeces. It contains undi- 
gested fats, carbohydrates, and proteins, as well as the 
products of bacterial action in the intestines — for the 
intestinal tract is always swarming with bacteria — and a 
certain amount of material from the digestive juices. The 
bacteria continue their action on the faeces outside the 
body; this is shown by the readiness with which manure 
rots when thrown into piles. 

Products of Combustion in the Body. — That portion of 
the food which is absorbed into the blood and used by 
the tissues furnishes a variety of waste products. The 
fats and carbohydrates are burned by means of the oxygen 
taken from the lungs; the carbon of these compounds 
(onus carbon dioxide and the hydrogen forms water, just 
as if they were burned in a fire outside the body. The 
carbon dioxide is thrown off through the lungs. The 
water is eliminated partly from the lungs, partly from 
the skin, and partly from the kidneys. During the per- 
formance of work by the muscle and nerve tissues and the 
consequent breaking down into waste products, the carbon 
of the proteins is partly converted into carbon dioxide and 
partly into compounds of nitrogen. The nitrogen is 
mostly con ve rted into urea, CON 2 H 4J which is discharged 
by the blood into the kidneys. This is the principal 
nitrogenous compound of the urine, and the one which 
80 easily undergoes ammoniacal fermentation outside the 
body (see p. 186) : The sulfur of the proteins appears in 
the urine mostly as sulfates. A variety of other com- 
pounds of nitrogen, carbon, hydrogen, and oxygen are also 
found in the urine, but there is no need of enumerating 
them here. 



QUESTIONS 243 

Summary. — From the above discussion we see that the 
maintenance of life and activity in the animal body in- 
volves a long series of complicated chemical changes. 
Only a few of these changes are known definitely; many 
others will no doubt be made known through future inves- 
tigations. It is evident even now that the animal body 
is a complex chemical factory, just as the plant body is. 
It contains delicate adjustments for burning just the right 
amount of fuel necessary to maintain the temperature 
at a certain definite degree. It contains organs for decom- 
posing and making soluble the raw material of the food. 
It contains transportation facilities for carrying the 
digested food material to every cell of the body. It is 
able to select just the right building stones for its various 
tissues. It can eliminate the unused portions and the 
waste products and thus keep the factory clear of obstruct- 
ing material. The better we understand the chemistry 
of our bodies, and of the bodies of our farm animals, the 
better will we be able to care for them, and the more will 
we appreciate the phenomena of the living organism. 

QUESTIONS 

1. State the most important processes that take place in the body. 

2. State what kinds of foods are used to keep these processes going. 

3. What is a calory of heat? How many calories are supplied by a one- 

pound loaf of bread? 

4. How many calories can be purchased for 10c. in the form of egg, 

butter, and potato, according to current prices in your neighborhood ? 

5. Why cannot sugar be used for building up muscle tissue? 

6. What elements does bone tissue require? 

7. Name the four classes of food substances. 

8. What is the object of digestion? 

9. Why cannot the body assimilate anything but water-soluble food? 

10. What substances are formed by the digestion of protein? Of fat? Of 

sucrose? Of milk sugar? 

11. What are enzymes? What kinds of enzymes are found in the mouth? 

In the stomach? In the pancreas? In the juice of the small intestine? 

12. What products are formed by the combustion in the body of fats? Of 

starch? Of protein? 

13. What are soaps? 

14. What kinds of waste materials are eliminated in the faeces, in the 

breath, in the perspiration, and in the urine? 



244 THE NUTRITION OF THE ANIMAL BODY 

LABORATORY EXPERIMENTS 

7g. To Study the Action of Ptyalin on Starch. — Make a solution of 
starch by boiling \g "it in 100 CC of water. Test 5 c.c. portions of it 
with iodine, and with Fehling's solution. Tlien place 5 e.e. of it in each of 
tnbes. To tube 1 add 2 c.c. of saliva; to tube 2 add 2 c.c. of boiled 
saliva; to tube 3 add 2 c.c. of -aliva and 1 drop of dilute hydrochloric acid: 
add 2 c.c. of water to the starch solution in tube 4. Allow all the tubes to 
stand for a half-hour in water warmed to the body temperature. Again test 
the contents of the tabes, using a few drops on a white dish for the iodine 
test and the rest for the Fehlintr test. What does each tube show? What 
happens to salivary digestion a^ soon as food reaches the acid contents of 
the stomach ! 

8o. To Show the Action of Pepsin on Boiled White of Egg. — Boil 
gg five minutes, then cut up the white, with the exception of a piece 
about one-fourth of an inch cube, into fine pieces. Dissolve 0.5 g. pre- 
pared pepsin scales in 50 c.c. of water. Then arrange the following 
test tubes: 

No. 1. — Fgg white — 10 c.c. of water. 

No. 2. — Egg white + 8 c.c. of water -f 2 c.c. of saliva. 

No. 3. — Eg? white + 10 c.c. of pepsin solution. 

No. 4. — Egg white + 10 c.c. of pepsin solution -f 2 drops of 5 per 

cent hydrochloric acid. 

No. 5. — Egg white -f- 10 c.c. of pepsin solution -j- 2 drops of 5 per 

cent sodium hydroxide solution. 

No. 6. — Large cube of egg white 4- 10 c.c. of pepsin solution -4- 2 
of egg white drops of 5 per cent hydrochloric acid. 

Keep in a place as near body temperature a* possible until the next day. 
Examine each tube carefully and state what each tube proves. To what 

3fl of food substances does egg white belong? 

8i. To Prepare Gelatin From Collagen. — Collagen is the protein 
found in bones. Place about 50 g. of fresh ground bone in a dish. Cover 
with water to which a few drop- of dilute hydrochloric acid have been added, 
cover the dish and boil gently for an hour, stirring occasionally, and re- 
placing the water lost by evaporation. Filter, and allow to cool. Save 
the boiled hone for experiment 83. If the filtrate does not set, boil it 
down to one-half it- volume and again allow to cool. To what class of food 
substances does gelatin belong? Test the gelatin according to the methods 
given in experiments 44 and 60. 

82. To Show the Composition of Egg-shell. — Boil pieces of egg-shell 
in water for a few minutes, pour off the water, and add a few c.c. of dilute 
hydrochloric arid. Result 1 Te>t the resulting solution for calcium ac- 
cording to the directions in experiment 52. Of what compound is egg-shell 
mainly composed 1 Mow do chickens obtain enough calcium to form 

ell s ? 

83. To Show the Composition of Bones. — Dissolve the boiled pieces of 
bone left from experiment §] in 50 CC. of dilute hydrochloric acid, warming 
it ne<- Dilute to L00 ce.. filter, and test portions of the filtrate for 
calcium and for phosphorus according to the directions in experiment 52. 



CHAPTER XVIII 

FOODS AXD FEEDS 

Coefficient of Digestibility. — From the discussion of 
digestion, assimilation, and elimination in the last chapter, 
it is evident that the food which is eaten follows two main 
routes through the body. One portion, which is not di- 
gested, passes through the intestinal tract and appears 
as faeces; the other portion, which is digested, passes 
through the various tissues of the body and appears as 
waste products in the urine, perspiration, and breath. 
The percentage of the food which does not appear in the 
fcEces is called the coefficient of digestibility. For exam- 
ple, let us take the figures obtained by studying the diges- 
tibility of clover hay when eaten by a cow : 

Protein Crude fiber Starch Fat 

Amount in 100 lbs. of hay . . 12.3 lbs. 34.8 lbs. 38.1 lbs. 3.3 lbs. 
Amount found in faeces.. 5.2 16.0 13.7 1.5 

Amount digested 7.1 18.8 24.4 1.8 

Coefficient of digestibility ^- = 58% 54% 64% 55%. 

It will be noticed that a considerable portion of each of the 
constituents is not digested. This will vary with the feed, 
and also with the kind of animal, as is shown in the table 
on page 246. Thus, a ruminant (cow or sheep) can 
digest only about 68 per cent of the protein of corn, 
whereas a pig can digest about 86 per cent of it. On the 
other hand, the cow can digest considerably more of the 
fat of corn than can the pig. 

Such figures on digestibility are only roughly correct, 
since individual animals differ widely in their digestion 

245 



246 



FOODS AND FEEDS 



capacities, and the chemical methods for the determina- 
tion of digestibility are not very accurate. 

Table XVIII 

Comparative Digestibility of Feeding Stuffs 





Kind of 

animal 


Coefficient of digestion 




Ash 


Protein 


Crude 
fiber 


Carbo- 
hydrates 


Fat 


Corameal 

Timothy hay. 
Potatoes 

Wheat bran .... 


Cow .... 
Horse . . . 
Pig 

Cow 
Horse . . . 

Cow... 
Horse . . 
Pig 

Cow 
Pig 


Per cent 

33 
34 

44 


Per cent 

68 
76 

86 

47 
21 

45 
88 
85 

78 
75 


Per cent 

29 

53 
43 

28 
33 


Per cent 

95 
96 

94 

62 

47 

90 
99 

98 

69 
65 


Per cent 

92 
73 

82 

52 
47 

13 

68 
72 



The Analysis of Foods and Feeds. — It is often highly 
desirable to know the composition of food materials in 
order to compute nutritive ratios and balanced rations, 
and to establish the money value of a product. Therefore 
the chemist has learned to make certain analyses of such 
products, which are designed to furnish an idea of the 
amount- of the various classes of substances present. 
These analyses are usually termed as follows: (1) Mois- 
ture; (2) ash; (3) crude protein ; (4) crude fiber; (5) ether 
extract; (6) nitrogen-free extract. The meaning of each 
of these terms will now be discussed. 

( 1 ) Moisture. — For this determination a weighed 
amount of the material in a dish is placed in an oven 
heated to the boiling point of water, and kept there until 
it no Longer Loses weight. The loss in weight is considered 
t«. represent the moisture content. It is evident that vola- 



THE ANALYSIS OF FOODS AND FEEDS 247 

tile substances other than water, such as the acids in 
silage, and odorous substances in many plant materials, 
will also be lost by this drying treatment. The error due to 
these causes, however, is seldom more than one per cent. 

(2) Ash.— This is determined by taking a weighed 
amount of the material, igniting it carefully in a special 
dish until there is nothing but a gray ash remaining. 
This is weighed, and the percentage of the whole which it 
represents is computed. In general, the ash represents 
the mineral matter of the feed; actually, however, it 
always contains some carbon as carbonate, which is not 
mineral matter; and some of the sulfur, which is a mineral 
element, is usually lost during the ignition. Therefore, 
the figures for ash give only an approximate idea of the 
mineral contents, but they are sufficiently exact for 
ordinary purposes. 

(3) Crude. Protein. — All proteins contain close to 16 
per cent of nitrogen. This figure is so constant that by 
determining the amount of nitrogen in a sample and 
multiplying it by 6.25, the amount of protein is obtained. 
In many feeds, for example hay, a good deal of the nitro- 
gen occurs in amids and amino acids. This nitrogen is, 
of course, included with that of the true protein in the 
analysis; hence the term, " crude protein." Since the 
forms of nitrogen have considerable nutritive value, there 
is no serious error involved in including them with the 
protein in our calculations. 

(4) Crude fiber is a term applied to certain of the cellu- 
lose constituents of plant material. It is determined by 
boiling the material in dilute acid, then in dilute alkali, and 
then drying and weighing whatever portion did not dis- 
solve in either of these. It is supposed to represent the 
indigestible portion of the feed. From Table XVIII, it 
will be seen that a considerable portion of the crude fiber is 
digested, however. This simply goes to show that a chemi- 



248 FOODS AND FEEDS 

cal process in the laboratory cannot imitate the processes 
of digestion in the animal. The only way to determine the 
value of a given food is to feed it to an animal and then 
measure the results by various means. 

(5) Ether Extract. — Fats are soluble in ether, but are 
not soluble in water. Therefore, by treating a sample 
of material with ether, the fat is removed. Then by 
evaporating off the ether, and weighing the fat that is 
left behind, an analysis of the sample for fat is obtained. 
Since, however, ether extracts other substances, such as 
chlorophyll, wax, and certain acids, the material obtained 
by the above analysis is more, correctly called " ether 
extract" than fat. In leafy material, such as hays and 
silage, the ether extract contains a large proportion of 
non-fat substances; in mill feeds and grains, the ether 
extract is practically all true fat. For the purposes of 
computing rations, however, it is sufficiently accurate to 
consider the ether extract as fat. 

(6) Nitrogen-free Extract. — When the above five 
analyses have been made, their sum is subtracted from 
100 per cent, and the difference is called the "nitrogen- 
free extract. " It is a poorly-chosen .term, as it gives no 
idea of the nature of the substances included under it. 
It is not an extract, and the crude fiber and the fat are 
also free of nitrogen. The water-soluble carbohydrates 
are the only substances not accounted for by the five 
preceding analyses. Instead of analyzing for starch and 
for sugars, which is a laborious process, these are in- 
cluded under the term nitrogen-free extract, assuming 
that in most plant materials starch and sugars do consti- 
tute the bulk of the portion remaining from the other five 
analyses. In feeds or foods in which sugar or starch is 
the characteristic constituent, such as syrups, molasses, 
and mill feeds, the individual carbohydrates are often 
determined. In this case they are not called "nitrogen- 



THE COMPOSITION OF HUMAN FOODS 



249 



tree extracts/' but are given their own designation, as 
sucrose, dextrose, and starch. 



Table XIX 

Composition of Some Common Foods as Percentages of the Edible Portion 



Apples 

Bananas 

Cherries 

Muskmelons 

Strawberries 

Tomatoes 

Asparagus 

Beans, string, fresh 

Beets 

Cabbage 

Corn, green 

Lettuce 

Peas, green 

Potatoes, white 

Potatoes, sweet 

Dates, dried 

Figs, dried 

Prunes, dried 

Beans, dried 

Flour, wheat 

Bread, white 

Beef, liver 

Beef, roast 

Beef, round, lean . . 

Eggs 

Ham, smoked, lean 

Mutton, leg 

Pork, chops.-. 

Oysters 

Whitefish 

Butter 

Chocolate 

Lard 

Walnuts 

Sugar, granulated . . 









Fuel value 


Protein 


Fat 


Carbo- 
hydrate 


per pound 
calories 


Per cent 


Per cent 


Per cent 




0.4 


0.5 


14.2 


285 


1.3 


0.6 


22.0 


447 


1.0 


0.8 


16.7 


354 


0.6 




9.3 


180 


1.0 


6.6 


7.4 


169 


0.9 


0.4 


3.9 


104 


1.8 


0.2 


3.3 


100 


2.3 


0.3 


7.4 


184 


2.3 


0.1 


7.4 


180 


1.6 


0.3 


5.6 


143 


2.8 


1.2 


19.0 


455 


1.2 


0.3 


2.9 


87 


7.0 


0.5 


16.9 


454 


2.2 


0.1 


18.4 


378 


1.8 


0.7 


27.4 


558 


2.1 


2.8 


78.4 


1575 


4.3 


0.3 


74.2 


1437 


2.1 


0.7 


73.3 


1368 


22.5 


1.8 


59.6 


1565 


11.4 


1.0 


75.1 


1610 


9.1 


1.6 


53.3 


1200 


20.4 


4.5 


1.7 


584 


22.3 


28.6 




1576 


21.3 


7.9 




694 


13.4 


10.5 




672 


19.8 


20.8 




1208 


19.8 


12.4 




863 


16.6 


30.1 




1530 


6.2 


1.2 


3.7 


228 


22.9 


6.5 




680 


1.0 


85.0 




3491 


12.9 


48.7 


30.2 


2768 




100.0 




4086 


18.4 


64.4 


13.0 


3182 






100.0 


1815 



The Composition of Human Foods. — In the accompany- 
ing table there are presented the analyses of some com- 
mon foods of several different groups. It is seen that 



250 FOODS AND FEEDS 

water is a very prominent constituent in most of them, 
especially vegetables. In fact, the percentage of water in 
most vegetables is as high or higher than that in milk. 
Even bread contains 30 per cent or more of water. 

Foods can be grouped in several ways. One way is on 
the basis of their origin — as vegetable foods, animal foods, 
manufactured foods. Another is on the basis of their 
characteristic constituent — as protein food, fatty food, 
and bulky food (containing much water and fiber). The 
latter basis is the one of most interest to us from the 
chemical viewpoint. Thus, there are the foods high in 
protein, such as lean meat, eggs, cheese, peas, and beans. 
It very often happens, as in eggs, that the percentage of 
protein in the whole product is low, due to the high water 
content; but that the greater portion of the dry matter 
present is protein. The commoner foods high in fat are, 
of course, lard, butter, olive oil, fat meats, and nuts. 
Some of the sugary foods are the syrups, sugar, and 
raisins. The starchy foods are cereal products and pota- 
toes. The foods highest in ash are the vegetables, espe- 
cially the leafy vegetables. 

The Composition of Feeding-stuffs. — The following table 
gives the analyses of some common animal feeds. What 
was said concerning the classification of human foods also 
holds true here, although feeds are usually roughly 
grouped into " concentrates' ' and "roughages." The 
latter contain much water and fiber, and the former rela- 
tively little of these things. The roughages are designed 
to give bulk to the food, so as to increase intestinal action, 
to supply a certain amount of nourishment at low cost, and 
to furnish the vitamines necessary for the growth and well- 
being of the animal. The concentrates, such as grains 
and mill feeds, are mostly used for forced feeding, to 
maintain high milk flow, or to hasten the fattening process. 
There is less range in composition among feeds than 



THE COMPOSITION OF FEEDING STUFFS 



251 



among the human foods — that is, there are none very 
high in fat, like butter and lard, and none high in protein, 
like cheese and lean meat. 

Table XX 

Composition of Some Common Feeding Stuffs 



Fodders : 

Corn fodder (green) . . . 

Corn fodder (field cured) 

Corn silage 

Timothy hay 

Alfalfa hay 

Clover hay (red) 

Roots : 

Turnips 

Rutabagas 

Grains : 

Corn 

Barley 

Oats 

Wheat 

Mill Products: 

Cornmeal 

Wheat bran 

Gluten feed 

Linseed meal (new 
process) 



Water 



Per cent 

79.3 
42.2 
79.1 
13.2 
8.4 
15.3 

90.5 

88.6 

10.9 
10.9 
11.0 
10.5 

15.0 
11.9 

7.8 

10.0 



Ash 



Per cent 

1.2 
2.7 
1.4 
4.4 
7.4 
6.2 

0.8 
1.2 

1.5 
2.4 
3.0 
1.8 

1.4 
5.8 
1.1 

5.2 



Crude 
protein 



Per cent 

1.8 
4.5 
1.7 
5.9 
14.3 
12.3 

1.1 
1.2 

10.5 
12.4 
11.8 
11.9 

9.2 
15.4 
24.0 

36.1 



Crude 
fiber 



Per cent 

5.0 
14.3 

6.0 
29.0 
25.0 
24.8 

1.2 
1.3 

2.1 

2.7 
9.5 
1.8 

1.9 
9.0 
5.3 

8.4 



Nitrogen- 
free 
extract 



Per cent 

12.2 
34.7 
11.0 
45.0 
42.7 
38.1 

6.2 
7.5 

69.6 
69.8 
59.7 
71.9 

68.7 
53.9 
51.2 

36.7 



Ether 
extract 



Per cent 

0.5 
1.6 
0.8 
2.5 
2.2 
3.3 

0.2 
0.2 

5.4 
1.8 
5.0 
2.1 

3.8 

4.0 

10.6 

3.6 



The legume hays are characterized by high protein, 
while the non-legume hays contain more carbohy- 
drates, such as starch, pentoses, and digestible cellulose. 
Although the fodders and hays appear to be high in ether 
extract in proportion to the small amount of dry matter, 
it must be remembered that the ether extract of these 
materials is composed largely of chlorophyll and wax 
instead of true fats, and hence is of less value to the ani- 
mal. This is shown in the table (p. 246), where the digesti- 
bility of the ether extract of the hays is far less than that 
of the grains. 



252 FOODS AND FEEDS 

Nutritive Ratio. — The fact was emphasized in the last 
chapter that the two main features in the life processes 
of the animal are the production of energy and the repair 
and formation of tissue. These two processes require 
different foods : the first can be supplied by carbohydrates, 
fats, and proteins, but the latter can be supplied only 
by protein. Since the protein element in foods is one 
of the most expensive, it is economy to supply just enough 
protein to maintain the growth and repair of tissue, and 
to utilize fats and carbohydrates for energy. Therefore, 
there has come into use the practice of computing the 
proportion of protein to non-protein constituents in a 
feed; this proportion is called the nutritive ratio, which 
can be denned as the ratio of digestible protein to diges- 
tible fats plus carbohydrates. 

Computing the Nutritive Ratio. — The nutritive ratio is 
computed as follows : In wheat bran, for example, there 
is 10.2 per cent digestible protein, 39.1 per cent digestible 
starch, 2.1 per cent digestible crude fiber, and 2.9 per cent 
digestible fat. Starch is taken as the unit for energy- 
producing food substances; and since a pound of fat is 
equivalent to 2.4 pounds of starch in fuel value, the fat 
in the above feed must be multiplied by 2.4 in computing 
the nutritive ratio. A pound of digestible fiber is taken 
as the equivalent of a pound of digestible starch. The 
ratio then becomes : 

digestible protein 
digestible starch + digestible fiber + (digestible fat X 2.4) 

or 

ifc? = m _ 1.47 

39.1 -I- 2.1 + (2.9 X 2.4) ~ 48.1 * ' 

The nutritive ratio is then 1 to 4.7. This means that for 
each part of digestible tissue-forming food there are 4.7 
parts of digestible energy-producing food. The term 
"wide ratio" is used for one like that of oat straw, about 



QUESTIONS 253 

1 : 12, where there is a small proportion of protein ; and 
" narrow ratio" for one like that of linseed cake, 1:4, 
where there is a high proportion of protein. 

A balanced ration is one in which the nutritive ratio 
of the feed is adjusted according to the needs of the 
animal. It is perfectly evident that all animals will not 
need the same proportion of protein to non-protein feed. 
Young animals, who are rapidly building up tissue, re- 
quire a higher proportion of protein ; that is, a narrower 
ration, than adult animals; and the younger the animal, 
the narrower the ration that is desired. Milch cows, 
manufacturing large quantities of protein in milk, require 
rather narrow rations. Horses or other animals at heavy 
work require narrower rations than those at light work. 
Balanced rations for all ages and kinds of animals, and 
for men at various kinds of work, have been very carefully 
worked out. Thus, a man at light work requires about 
2500 calories of energy per day, and a nutritive ratio of 
about 1 to 8; a man at heavy work requires about 3500 
calories, with a nutritive ratio of about 1 to 6; a young 
growing animal, a nutritive ratio of 1 to 5, a milch cow 
1 to 6 : 5 or 7. More details concerning the feed re- 
quirements of animals can be obtained from books on 
stock feeding. 

Since it is not the purpose of this book nor of this 
course to discuss the details of feeding practices, but only 
to give the chemistry underlying such practices and the 
theories governing them, we will not go more deeply into 
the subject of foods and nutrition, except to discuss cook- 
ing and preserving processes. 

QUESTIONS 

1. Why cannot a chemical analysis of the food tell us its digestibility? 

2. How is the digestibility of a feed found? How do chemical analyses 

help in this? 

3. Explain how each of the following is determined in analyzing a food: 

water, protein, fat, fiber, ash, and carbohydrates. 



254 FOODS AND FEEDS 

4. What is the difference between " ether extract " and " true fat "? 

5. Name several foods which have a higher water content than that of milk, 
(i. Why is clover hay preferable to timothy hay for milch cows? 

7. What are "concentrates"? 

S. What purpose do roughages serve in animal nutrition? Name some 

roughages among human foods. 
9. In computing nutritive ratios, why are fats and carbohydrates figured 

together? Why is the per cent of fat multiplied by 2.4? 
10. Does a laying hen need a wide or a narrow nutritive ratio? Why? 

LABORATORY EXPERIMENTS 

84. To Determine the Amount of Moisture in a Food Material.— 
Weigh accurately about 10 g. of sliced potato, carrot, beet, cabbage leaves, 
apple, or other similar succulent food, in a shallow aluminum, tin, glass, or 
other dish that has been previously accurately weighed. Place in an oven 
heated to 100° C. After 6 or 8 hours, cool quickly and weigh. Place in the 
oven again for an hour, and reweigh. Repeat until no loss in weight 
occurs. The loss in weight represents moisture. Calculate the percentage oi 
moisture in the food. Save the dried residue for the next experiment. 

85. To Determine the Amount of Ash in a Food Material. — Accu- 
rately weigh a porcelain dish about 2 or 3 inches in diameter. Place in it 
the dried residue from experiment 84, and carefully ignite with a hot 
flame until only a white or gray ash remains. Cool and weigh. Calculate 
the amount of ash in the dried material and in the original fresh material. 
What elements compose this ash? 

86. To Show the Presence of Fat in a Food Material. — Place about 
g. of cornmeal in the drying oven for 2 or 3 hours. Place it in a small 
beaker, and cover with ether. (CAUTION: keep at least 10 feet from 
flames!) Allow to stand with occasional stirring for 15 minutes. Filter 
off the ether through a paper and evaporate it to dryness in a small beaker 
in a warm place away from flames. What is the residue in the beaker? 
How could the total ether extract in a food be determined? Make a similar 
extract of dried and finely chopped alfalfa hay. To what is the color due? 
How does the ether extract of the hay and of the corn differ? 

87. To Determine the Amount of Crude Fiber in Hay. — (a) Accu- 
rately weigh 5 g. of finely chopped alfalfa hay. Place in a beaker with 200 
c.c. of 1.25 per cent sulfuric acid and boil for" 30 minutes. Filter through a 
piece of linen cloth, wash with a little water, transfer the residue to the 
beaker again and boil 30 minutes with 200 c.c. of 1.25 per cent sodium 
hydroxide. Again filter through the linen cloth, wash with hot 1.25 per 
cent sulfuric acid, then with hot water until the wash water is colorless. 
Transfer the residue to a small weighed dish, dry in the oven at 100° C. 
and weigh. Tne final dried residue is the crude fiber of the hay, and 
represent approximately the indigestible carbohydrates. It is mostly cellu- 
lose. Calculate the percentage of crude fiber in the hay. 

(bi How is the protein in a substance determined? The nitrogen- 
free extract? 



CHAPTER XIX 

CHEMISTRY OF THE COOKING AND PRESERV- 
ING OF FOODS 

So far in our discussion of the nutrients used by both 
man and the lower animals, no account has been taken 
of the effect on their composition by the ordinary pro- 
cesses of handling to which they are subjected. The 
majority of human foods are cooked; some animal feeds 
are cooked; and many of our foods are subjected to 
methods of preservation. These processes involve 
chemical changes; and since chemical changes in food 
constituents may affect their value as foods, we should 
have an understanding of the chemistry involved in the 
cooking and preserving of food. Furthermore, the 
clearer our knowledge of these processes is, the more 
effectively can we perform and control them. 

Effect of Heat. — The heating of most food substances 
improves their palatability ; that is, it imparts to them 
agreeable flavors ana odors which stimulate the appetite 
and excite the flow of digestive juices. In these respects, 
cooking is very important and beneficial. Its effect on 
some of the food constituents may not be so beneficial. 

(1) The effect of heat on proteins is to coagulate them. 
The familiar example of this is the boiling of an egg 
whereby both the white and the yolk are congealed or 
coagulated to a solid. All proteins are thus affected by 
temperatures above 150° F. There has been a great 
deal of discussion and experimenting concerning the rela- 
tive digestibility of cooked and of uncooked proteins, some 
maintaining that the coagulation increases the digestibil- 

255 



256 COOKING AND PRESERVING OF FOODS 

ity, others that it decreases it. However, it is now pretty 
generally agreed that the digestibility is decreased. For 
this reason raw eggs are always recommended for inva- 
lids. As regards the proteins of meat, their digestibility 
is also decreased by cooking; but what more than offsets 
this is the fact that the cooking makes the meat more ten- 
der and hence can be better chewed, and that the marked 
improvement in flavor stimulates the digestive processes. 
This is often the deciding point in the question of whether 
hog feeds should be fed cooked or raw. Although the per- 
centage of nutrients digested may be less in the cooked, 
the animals eat more, and hence it is conomy to feed the 
cooked food. 

The coagulation of proteins by heat furnishes the 
explanation of certain cooking practices. Vegetables are 
always started cooking in boiling water, as the outer layers 
are then coagulated immediately, which prevents the 
extraction of materials from the inner tissues. Likewise, 
meat for soup is put into cold water and brought slowly 
to boiling, so as to extract as much material as possible 
from the meat ; while meat for boiling and for roasting is 
seared with boiling water at the beginning. 

(2) Effect of Heat on Fat.— If clear, separated fat, such 
as lard or butter, is heated rather highly, it becomes 
brownish in color, and gives off irritating odors. These 
odors are due to a decomposition product of the glycerin, 
called acrolein. Such a change in fats should be avoided, 
as it impairs their palatability. When fatty tissue is 
lien ted, the effect is to liberate the fat from the connective 
tissues by which it is surrounded. This is well illustrated 
in the ' ' trying out ' ' of lard ; the ' i cracklings ' ' are the pro- 
tcin connective tissues. Thus the composition of the fat 
in roasted meat itself is not changed; it is simply made 
more accessible to the digestive juices and more palatable 
by the changes in the tissues enclosing it. 



EFFECT OF DIFFERENT METHODS OF COOKING 257 

(3) Effect of Heat on Carbohydrates. — Heat itself does 
not affect the sugars. If, however, sucrose is boiled in the 
presence of acids, it is hydrolyzed into dextrose and levu- 
lose (p. 213). This takes place in jelly-making. In mak- 
ing certain kinds of candy this reaction is also brought 
about by the addition of cream of tartar (a form of tartaric 
acid). The polysaccharides, especially starch, undergo 
very important changes during heating. Starch is insolu- 
ble in cold water, but on boiling it is converted into starch 
paste, a semi-soluble form. The raw starch is very diffi- 
cult to digest by man, hence the necessity of thoroughly 
cooking vegetables and cereals. When starch is exposed 
to dry heat, as in baking bread or cake, it is converted into 
dextrin (p. 211), which is indicated by the brown crust. 
Dextrin is somewhat more easily digested than starch. 

Effect of Different Methods of Cooking. — The above dis- 
cussion pertains only to the individual constituents of 
foods. What changes occur in the composition of a food 
during the ordinary processes of preparation and cook- 
ing? In the first place, as regards the boiling of vege- 
tables, it has been found that a large proportion of the 
mineral elements is removed in the peelings and that a 
further large proportion of minerals, besides starch, 
sugars, and flavoring matter, is removed during the boil- 
ing, even though the precaution is taken to sear the vege- 
tables with boiling water at the start. The obvious ways 
of preventing these losses of nutrients are to boil potatoes 
' ' with the jackets on," and to boil down other vegetables 
to a small volume of water and then to include this water 
with the vegetables when served. When meat is boiled, 
the materials extracted are not wasted but are used in 
soup or in gravy. 

Frying consists in heating the food rather highly in fat. 
If the temperature at the start is rather high, the proteins 
of the food, either meat or vegetable, are coagulated to 
17 



258 COOKING AND PRESERVING OF FOODS 

a considerable degree, and this prevents the fat from 
soaking into the food. If, however, the proteins are not 
coagulated at the start, or if it is a cereal food compara- 
tively low in protein, a great deal of fat is absorbed. It 
has been found that doughnuts which contain 5 per cent 
of fat before frying, contain as high as 20 per cent after 
frying. This absorption of fat around the particles of 
the food hinders mouth and stomach digestion, since the 
fats are digested only in the intestine, and they shield 
the proteins and starch from the digestive juices of these 
two organs. 

Roasting and baking are the most ideal methods of cook- 
ing vegetables, meat, or dough foods. A dry or a moist 
heat can be used, a high or a low temperature, none of the 
nutrients are lost by extraction with water, and the flavors 
developed are usually superior to those in either frying 
or boiling. 

Leavening Agents. — TVhen a dough is made of flour, 
water, and salt, and then baked, the product is exceedingly 
hard and flinty. Examples of such foods are hardtack and 
macaroni. If, however, a leavening agent is added to the 
dough, a light, soft, porous product results. A leavening 
agent is one which supplies gas to the dough in the form 
of minute bubbles ; and these bubbles, expanded by the 
heat of baking, puff up the dough into a porous mass. 
Some of the commonest materials in use for leavening 
I tin-] )<)><-> are yeast, baking powder, baking soda, and 
white of egg. 

ill Yeast is a mass of living, microscopic plants. It 
feeds on sugars, especially dextrose, and gives off as by- 
products of its life processes carbon dioxide and alcohol. 
This can !)•' represented by the following equation: 

( U." = 2C.H.0 + 2 CO,, 

dexti alcohol carbon dioxide 



LEAVENING AGENTS 



259 



When the yeast is mixed with the dough and allowed to 
stand in a warm place, the yeast grows and multiplies, 
producing carbon dioxide gas. This gas is held by the 
elasticity of the gluten of the flour just as rubber balloons 
are expanded with air, with the result that the dough is 
filled with minute bubbles of gas. On baking, the bubbles 




Fig. 62. — Bread-making contest at a state fair. Trie making of good bread is both an art 

and a science. The latter phase of it involves certain definite chemical reactions, which 

must be understood by the successful bread-maker. 

expand still more, which distends the whole mass of dough 
to several times the original volume. The temperature 
of the oven vaporizes all the alcohol, so that the bread is 
entirely free from it. The sugar or the potato water added 
to bread doughs is for the purpose of feeding the yeast, 
as the latter feeds but very slowly on the raw starch of 
the dough. The baking of bread receives a great deal of 
attention in this country, as is evidenced by the scene in 
Fig. 62. (See also Fig. 63.) 



260 



COOKING AND PRESERVING OF FOODS 





3- — The development of the flour milling industry. On the top, left, is a picture of 

;ng wheat between two stones, a method used for thousands of 

i Dutch windmill. Millstones are also the grinding medium here. 

- of one of the largest modern roller mills. The grain is reduced to flour 

: long series of steel rollers. By this treatment the bran layers are broken 



■ .~«.. B srti ico ui oicrn i unci ?. t>\ mi;? ireauueui iue urau ia\ tis are uru^eu 

ind hrnre ran easily be sifted from the powdered starch v portions of the grain. 

- three grades of flour, and several kinds of stock feed, result from wheat by this 



LEAVENING AGENTS 261 

(2) Baking poivders are mixtures of chemicals which, 
when they come in contact with water, liberate carbon 
dioxide. This serves to leaven dough in the same way as 
the carbon dioxide from yeast. We have seen previously 
(p. 132) that when an acid reacts with a carbonate, carbon 
dioxide is produced. This reaction is utilized in baking 
powders. These always contain two active ingredients : 
baking soda (sodium bicarbonate, NaHCO a ) and an acid. 
The acids commonlv used are tartaric acid, H 2 C 4 H 4 6 ; 
cream of tartar, KHC 4 H 4 6 ; alum, K 2 S0 4 .A1 2 (S0 4 ) 3 .24- 
H 2 ; and an acid phosphate, as NaH 2 P0 4 . The equation 
for the reaction in the case of the tartaric acid powder 
is as follows : 

+ co 2 + H 2 o 



ILC 4 H 4 Oe 


+ 


2 NaHC0 3 = 


= Na 2 OH 4 6 


tartaric 




sodium 


sodium 


acid 




bicarbonate 


tartrate 



Thus there is formed sodium tartrate, carbon dioxide, and 
water. The sodium tartrate is a harmless salt, and is 
present in quantities too small to impart a taste to the 
dough. Similar reactions occur in each of the other types 
of baking powder, there being always formed carbon diox- 
ide, water, and a salt. 

It is obvious from the above reactions that definite 
quantities of the active substances react; thus 150 parts 
by weight of tartaric acid react with 164 parts of baking 
soda ; or for each ounce of the acid there must be 1.1 ounces 
of soda. In this way proportions are computed for each 
of the types of baking powders. 

In addition to the active constituents, there is always 
added a certain amount of ' ' drier, ' ' usually starch, to the 
extent of from 10 to 40 per cent. This is to keep moisture 
away from the active constituents, which do not react with 
each other until moisture is present. 

(3) Soda, or sodium bicarbonate, is used very often 
as a leavening agent in connection with foods which con- 



262 COOKING AND PRESERVING OF FOODS 

tain acid, such as sour milk, vinegar, and molasses. The 
reaction is the same as in the baking powders, although 
the kinds of acids are different, and hence also the kinds 
of salts left behind in the dough. 

(4) When white of egg is beaten to a foam, the foam 
consists of a small amount of protein surrounding a large 
amount of air in the form of minute bubbles. When this 
beaten egg is mixed into a cake dough and baked, the 
expansion of these air bubbles serves as a leavening agent. 
The greater the amount of egg white used, the greater 
will be the leavening effect. 

Preservation of Food. — What is usually meant by the 
spoiling of food is its decomposition by the growth of 
microorganisms, such as molds, yeast, and bacteria. 
Therefore the preservation of food consists in the preven- 
tion of this action of microorganisms. In order for these 
organisms to thrive, several conditions must be met: (1) 
there must be a proper temperature; (2) there must be 
sufficient moisture; (3) there must be food of the proper 
kind and amount; (4) there must not be any poisonous 
chemicals present in the food. By controlling these four 
conditions to the disadvantage of the organisms, the latter 
can be prevented from spoiling food or any other product. 

(1 ) The temperature at which most bacteria and molds 
can live and thrive is between 40° F. and 120° F. // the 
temperature is above this limit, the organisms are soon 
killed; if it is below this limit, they are not killed but, 
remain inactive. It is for this reason that high and low 
temperatures are used to such a great extent for the 
preservation of food. Heating the material for some time, 
i specially at the boiling-point of water or higher, steril- 
izes it, and this is the universal process in the manufac- 
ture of canned foods (Fig. 64). In the case of some organ- 
isms which form heat-resisting spores, it requires several 
hours of boiling to produce sterilization. Holding the 



PRESERVATION OF FOOD 



263 




Fig. 64. — Sterilization by means of steam of trucks used in handling meat. Heat, and 

especially moist heat, is one of the cheapest and most effective disinfecting agents there is. 

Milk vessels are sometimes sterilized in a similar manner. 



264 



COOKING AND PRESERVING OF FOODS 



food ill cold storage, especially below the freezing-point 
of water, is a very effective way of preserving foods as 
meat and butter, which must be kept in an uncooked, fresh 




— Gnun elevators. These have a capacity of 112,000 bushels of grain, with machin- 
ing and stirring the grain to prevent its heating. Heating is accompanied by 
chemical changes which impair the germination and, in the case of wheat in particular, its 

milling value. 

condition. Eggs, fruits, and vegetables must be kept at a 
temperature Blightly higher than freezing. 

(2) The amount oj moisture which a food must con- 
tain before it will be likely to spoil varies greatly, accord- 
ing t<» tie* kind of food and the type of organisms. The 



PRESERVATION OF FOOD 



265 



only point that interests us is the fact that when fruits, 
meats, vegetables, and other food products are dried to 
a certain low moisture content (usually between 10 and 
30 per cent), microorganisms cannot thrive in them. Some 
of our great food industries are engaged in the drying of 




Fig. 66. — Interior of smoke-house. After pickling the hams in salt and saltpeter, they are 

Bubjected to birch wood smoke. This smoke contains compounds somewhat similar to 

creosote and carbolic acid, which prevent the growth of bacteria. 

prunes, peaches, apples, raisins, and other fruits; while 
the dehydration of vegetables has come into prominence 
due to a war necessity. The Indians have always pre- 
served meat by drying. New grain must have its moisture 
content reduced to about 12.5 per cent, else enzyme action 
will develop enough heat to spoil the grain (Fig. 65). 



266 



COOKING AND PRESERVING OF FOODS 



(3) There is such a thing as a product containing 
too much sugar for the normal activities of bacteria and 
yeasts. Thus, when these organisms attempt to grow on 
jells and jams, their delicate cells are destroyed by contact 
with the strong sugar solutions. 

(4) Poisonous chemicals for killing microorganisms 




Fig. 67. -Curing room for hams. The fresh hams are pickled for some weeks in a solution 

of salt, saltpeter (sodium nitrate), and sugar. These permeate throughout the meat, and 

not only flavor it but preserve it. They are then smoked; the constituents of the smoke 

act as a further preservative. 

are given various names, according to their use, as germi- 
cides, disinfectants, antiseptics, and chemical preserva- 
tives. The latter term is the usual one applied to food 
products. We can conveniently classify the chemical pre- 
servatives into two groups: those which are in good re- 



PRESERVATION OF FOOD 



267 



pute, and those which are in bad repute. Those which are 
in good repute and which are widely used for the preser- 
vation of meat and fish in particular, are common salt, 
saltpeter, and smoke. Salt pork, corned beef, salted fish, 
and smoked pork and fish owe their keeping qualities to the 
presence of these substances, which are poisonous to bac- 
teria (Figs. 66 and 67). The smoke contains chemical 
substances related to creosote. Other harmless preserva- 




Fig. 68. — A pair of modern silos. In these huge containers the green plant undergoes 
fermentative changes which preserve the fodder in a fresh and succulent condition for many 

months. 

tives are vinegar for pickles and water glass for eggs. 
Silage is green fodder which is kept from spoiling by the 
development of acids and the exhaustion of the oxygen in 
the silo (Fig. 68). 

Certain other chemicals, which are not only poisonous 
to the bacteria, but also to man if taken in anything but 
small quantities, are sometimes used to prevent the spoil- 
ing of food. The commonest preservatives of this class 
are formaldehyde, boric acid, benzoic acid, and sulfites. 
Practically all state governments as well as the national 



268 COOKING AND PRESERVING OF FOODS 

government have stringent laws against the use of such 
preservatives in food products. The objection to them is 
not based so much on their harmfulness to those who con- 
sume them, but on the fact that their use enables the 
manufacturer to use spoiled and inferior raw materials, 
and to be careless in his methods of handling them. In 
order to protect the purchaser, the food laws require that 
if a preservative be used in a food, it shall be so stated 
on the outside of the package. One of the most frequent 
violations of this law is the use of formaldehyde in milk to 
prevent its souring. 

QUESTIONS 

1. Why is it desirable to eat foods which have agreeable flavors and odors? 

2. What does heat do to proteins? How does this affect their digestibility? 

3. In broiling a steak, why should it be seared on both sides on a hot 

griddle at the start? 

4. Write an equation showing the effect of boiling sucrose in the presence 

of an acid. 

5. Why should all vegetables be thoroughly cooked? 

6. What is the brown substance which forms on toast? 

7. Why should potatoes be boiled " with the jackets on "? 

8. What is yeast? Name two great industries which make use of yeast 

fermentation (see -equation pp. 74 and 258). 
1>. What three constituents do all baking powders contain? What is the 
purpose of each? 

10. Devise a recipe for mixing up five pounds of tartaric acid baking pow- 

der, allowing for 15 per cent of starch in it. 

11. What takes place when sour milk and soda are used in the same bat- 

ter? What product is left behind? 

12. Xame the four factors which govern the life activities of bacteria and 

molds. Describe how apples might be preserved by five differ- 
ent methods. 

13. State two objections to the use of chemical preservatives in the canning 

of food. 

LABORATORY EXPERIMENTS 

88. To Show the Effect of Heat on Protein.— Dissolve the white of 
an egg hi .") times its volume of water. Divide into. two portions. Heat one 
portion in a test tube or small beaker very slowly, shaking frequently. 
When a cloudiness in the solution shows that the protein is being coagu- 
lated, remove from the flame and quickly take the temperature of the 
solution. \<>w heat the other half of the egg-white solution to a temperature 
"' : ' C. less than the temperature at which the first portion coagulated. 
Keep it al this temperature for some time. Why does not the protein 
coagulate? Wha1 do you infer from this concerning the condition of the pro- 



LABORATORY EXPERIMENTS 269 

tein in the center of a piece of "rare" roast beef? Which are probably 
the more digestible, coagulated or uncoagnlated proteins? 

89. To Show the Effect of Dry Heat on Starch.— Carefully remove 
about 0.5 gram of the very outer crust of some very well browned bread. 
Crumble it up fine and suspend in 100 c.c.of water. Suspend a similar amount 
of the crumbled white portion of the bread in 100 c.c. of water. Boil both so- 
lutions a few moments, cool and add 3 drops of iodine solution to each. 
Judged by the intensity of color in the two solutions, has the browning of 
the bread destroyed any of the starch ? Into what was it converted ? 

What is the effect of moist heat (that is, boiling) on raw starch? 
Compare with experiments 66 (a) and 67 (b). 

90. To Prepare a Baking Powder. — Dissolve a very small amount of 
tartaric acid in a few c.c. of water. Does any action take place? Dissolve 
a similar amount of baking soda in water. Any reaction? Thoroughly 
mix equal portions of dry tartaric acid and baking soda, and then add the 
mixture to water. Reaction? Add the solution of tartaric acid prepared 
in the first place to the solution of baking soda. Reaction? What gas is 
given off? Test it with a burning match. Test it with a drop of clear 
limewater on the end of a clean glass rod. What do these tests show? 
What is a baking powder? Why must moisture be kept away from such 
powders? How are commercial baking powders usually kept dry? Com- 
pare the chemistry of baking powders with that of chemical 
fire extinguishers. 

91. To Show the Effect of Temperature and of Preservation on the 
Keeping Qualities of Milk. — Arrange the following series of test tubes: 

(a) 10 c.c. of milk. 

(b) 10 c.c. of milk stood in a beaker of boiling water for 10 minutes. 

(c) 10 c.c. of milk and one drop of hydrogen peroxide. 

(d) 10 c.c. of milk and one drop of dilute formaldehyde solution. 
Place these tubes in a warm place (25 to 30° C.) and examine at 

frequent intervals to see when they become curdled. Label a fifth tube 
(e) and put in it 10 c.c. of fresh milk, store in a cool or cold place, and 
note the progress of souring. Name three effective ways of preserving milk 
shown by this experiment. Which of these is the least desirable, and why? 



CHAPTER XX 

MILK AND ITS PRODUCTS 

Milk is the secretion of the mammary glands of mam- 
mals. It is elaborated as a food especially adapted to the 
needs of young animals. A brief discussion of its chemical 
composition and characteristics will serve to impress us 
with the fact that it is a most remarkable fluid, and will 
also show why the civilized nations have developed the 
dairy cow and her products so extensively (Fig. 69). 

Secretion of Milk. — Milk is a mixture of many different 
substances. These substances are manufactured by the 
cells of the udder, out of raw materials supplied by the 
blood. Every judge of dairy cows knows how richly the 
udder is supplied with blood-vessels. This is very neces- 
sary, for the milk is not manufactured by the udder con- 
tinuously between milkings, but is formed mostly during 
the operation of milking; hence the blood must bring to 
the cells an abundant supply of raw materials. Xow the 
interesting and remarkable fact about this formation of 
milk from the substances in the blood is, that the milk 
constituents themselves are not found in the blood, nor 
in fact in any other part of the body. Thus, the fat of 
milk is different entirely from the fat of any other part 
of the body ; the casein is different from the blood proteins ; 
and milk sugar is not found in any other part of the body 
or in any plant body. Therefore the cells of the mammary 
gland must take the fatty acids and glycerin which the 
blood brings from the digested food and remake them 
into the particular kind of fat wanted in the milk. And 
they must sort out the amino acids of the blood and com- 

270 



SECRETION OF MILK 



271 



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272 MILK AND ITS PRODUCTS 

bine the proper ones into casein; and so on for all the 
constituents of milk. Furthermore, the mineral elements 
in milk are in entirely different proportions from what 
they are in blood. 

Constituents of Milk. — The principal constituents of 
milk are water, sugar, proteins, fat, and ash. 

The sugar found in milk is lactose. This belongs to 
the dihexose group, having the formula C^H^On. When 
it is acted upon by the digestive juices it is hydrolyzed 
as follows (see p. 213) : 

C„H„O n + H.,,0 = C 6 H I2 O + OB^O, 
lactose dextrose galactose 

Milk sugar is very much less sweet than cane sugar. It 
is not fermented into alcohol and carbon dioxide by ordi- 
nary yeast, although it is by certain other yeasts. It used 
to be thought that lactose is more readily digested and less 
easily undergoes acid fermentation in the digestive 
tract than cane sugar. This does not appear to be 
the case, however. 

Lactose is very quickly converted into lactic acid, 
C 3 H 6 3 , by the so-called sour milk bacteria. This acid 
causes the curdling of milk. In fresh milk there is about 
0.2 per cent lactic acid; when the acidity has reached 0.4 
per cent, a sour taste is perceptible ; at 0.7 per cent curd- 
ling can be seen. The acidity may go as high as 2.0 per 
cent after long scouring. 

The proteins of milk are- casein and albumin. The 
casein gives milk its chalky-white appearance. Besides 
being composed of carbon, hydrogen, oxygen, nitrogen, 
and sulfur, like all other proteins, casein is unusual in that 
it is also combined with calcium and phosphorus. 

Casein can be made to precipitate out, or curdle, by two 
different methods. One of them is by adding an acid to the 
milk. This takes calcium away from the casein, and the 



CONSTITUENTS OF MILK 273 

latter then becomes insoluble. This is what happens dur- 
ing the ordinary souring of milk. The other way of curd- 
ling milk is by means of the enzyme called rennin, found 
in the stomachs of all animals. In this case calcium is 
not abstracted from the casein ; in fact, calcium must be 
present in the milk or curdling will not take place. Why 
nature has provided for the curdling of milk as soon as it 
enters the stomach is not known. It no doubt has some- 
thing to do with the ease and completeness of digestion. 
Rennin is prepared commercially from the stomach of 
calves, pigs, and sheep, for use in cheese factories. 

The albumin in milk is in solution and hence is invisir 
ble. It is not coagulated by acids nor by renning, but it is 
coagulated by Heat. Thus it always remains in the whey, 
where it can be seen if the whey is boiled. The albumin 
does not contain calcium or phosphorus. 

Butter-fat is a mixture of a number of fats. Some of 
these fats are found in no other plant or animal fat, and 
give to butter-fat some of its characteristic properties, 
such as its power to absorb odors, and its penetrating odor 
when rancid. These particular fats are lacking in oleo- 
margarine, and this constitutes the principal means of 
distinguishing butter from margarines. 

Fat occurs in milk in minute globules. These globules 
are larger in the milk of Jerseys and of Guernseys than 
in that of other breeds, hence the cream in the milk of these 
breeds rises more quickly than in the latter. 

The ash of milk consists of the following eight ele- 
ments: calcium, magnesium, potassium, sodium, sulfur, 
phosphorus, chlorine, and a trace of iron. Whole milk 
contains about 0.72 per cent of ash. Of this, about one- 
fourth is potassium, one-fourth phosphorus, one-fifth cal- 
cium, and smaller amounts of the other elements. These 
are the mineral elements necessary for animal life, as we 
saw in Chapter XI ; we would therefore expect milk, which 

18 



274 MILK AND ITS PRODUCTS 

serves as the sole food for young animals, to contain them. 
Composition of Milk. — The amounts of the above con- 
stituents in cows' milk vary considerably, according to 
breed, period of lactation, age, and individuality. The 
following is the average composition, compiled from thou- 
sands of analvses of American milks : 





Per cent 


Per cent 


Water 


87.1 Casein 


2.6 


Sugar 


5.1 Albumin 


0.6 


Fat 


3.9 Ash 


0.7 



The fat is the constituent most subject to variation, it 
being frequently as low as 2.0 per cent and as high as 
9.0 per cent. 

Effect of Breed on Composition of Milk. — One of the 
factors affecting the composition of milk is the breed of 
animal. The Jerseys and Guernseys produce milk that 
averages over 5.0 per cent of fat, and 3.0 per cent of 
casein; while the milk of Holsteins usually contains not 
over 3.4 per cent fat and 2.2 per cent casein. Since the 
latter breed produces greater quantities of milk per cow, 
however, the total output of milk solids does not vary a 
great deal among high-grade animals of the various 
dairy breeds. 

Individual Variation Among Cows. — What is of more 
significance to the dairyman than breed is the production 
by the individual cow. No two cows of the same breed and 
age, and eating the same food, will produce milk of the 
same composition. And the differences between them 
may be very great, the total solids being as low as 9 per 
cent and as high as 15 per cent. Usually feed and care 
will help the poor producer to only a limited extent. Hence 
the practice that has come into vogue of testing the com- 
position of the milk from individual cows, especially foi 
the fat content, so as to provide a basis for weeding out 
the unprofitable ones (Fig. 70). 



INFLUENCE OF FEED ON COMPOSITION OF MILK 



275 



Effect of Stage of Lactation. — The period of lactation 
affects the composition of milk to a considerable degree. 
The first milk, or colostrum, is very high in albumin, con- 
taining 12.0 per cent or more of this protein. The colos- 
trum gradually changes to normal milk in eight or ten 
days. During the first month the fat and casein are some- 
what high; these show a decrease during the second and 




Fig. 70. — Outfit for testing milk on the farm. With this, equipment and a bulletin of 

.directions from the state agricultural experiment station, a farmer can test the milk of each 

cow for butter-fat at frequent intervals, and thus determine which animals are profitable 

and which are not. (From Circular 78, Purdue Sta.) 



third months, followed by a gradual increase up to the end 
of the lactation period. 

Influence of Feed on Composition of Milk. — The feed may 
affect the quantity of milk produced, but it exercises but 
very little effect on the composition. This has been proved 
again and again at various agricultural experiment sta- 
tions, since the proposition of feeding cows in a particular 
way in order to increase the per cent of fat is an ever- 
recurring one. In one experiment a herd of cows were 
poorly fed for a while, and then liberally fed. During 
the latter period the total flow of milk w x as greatly in- 
creased, but the percentage of constituents remained prac- 
tically the same, except for a very slight increase in fat. 
As has been mentioned before, the fats in certain kinds 



276 MILK AND ITS PRODUCTS 

of feed produce butter-fats of different degrees of hard- 
ness. Tims cottonseed meal produces a harder butter-fat, 
of lower melting point, while gluten feed, rich in oil, pro- 
duces a softer butter. Similarly, early spring grass pro- 
duces softer butter. 

Butter. — The first step in the process of making butter 
from milk is the separation of the cream. This is now 
usually done by centrifugal force in i i separators. ' ' The 
amount of fat in the cream can be varied at will, but for 
butter-making it is usually between 20 and 35 per cent. 
Only 0.05 to 0.10 per cent of fat is left in the skim-milk. 

The fresh cream is " ripened" or allowed to sour, in 
order to produce the characteristic butter flavor and odors. 
This ripening is brought about by the ordinary lactic acid 
bacteria found in milk. In many creameries the cream is 
first pasteurized by heating to 145° F. for 15 or 20 minutes 
to kill most of the harmful bacteria, It is then inoculated 
with a pure culture of sour milk bacteria called a 
"starter" and allowed to ripen. When the acidity has 
risen to about 0.5 per cent the cream is churned. This 
brings about a separation of the fat from the rest of the 
milk. When the fat grains have reached a certain size the 
buttermilk is drained away, the butter washed, and then 
salted. This process leaves but a small amount of milk 
solids (mostly casein and lactose) in the butter. The 
latter is composed on the average of about 80 to 85 per 
cent of fat, 12 to 15 per cent of water, 0.6 to 1.4 per cent 
of casein, and 2.0 to 4.0 per cent of salt. 

Cheese. — This dairy product has been made since 
ancient times from the milk of cows, goats, sheep, camels, 
;!ii<l mares. The essential processes are the curdling of the 
milk by means of the enzyme rennin, which is extracted 
from calves' stomachs, the separation of the curd from 
the whey, the pressing of the curd into molds, and then 
ripening the product for some weeks or months. It is 



QUESTIONS 



277 



during this ripening that the characteristic flavors are 
developed, due to the action of various bacteria and molds. 
The principal variation in the composition of cheeses is in 
the fats, as they may be made from milks of widely differ- 
ing fat content, from partially skimmed milk to cream. 
As the casein coagulates, the curd brings down with it 
most of the fat, together with a little of the milk sugar 
and ash. 

Comparison of Dairy Products. — For the sake of compar- 
ing the various products made from milk, the accompany- 
ing table has been prepared. The fact of greatest signifi- 
cance seen in these data is that all of these products are 
very high in food substances. And this, together with the 
fact that the fats, proteins, and carbohydrates of these 
products have very high coefficients of digestibility, shows 
that the reputation of these substances as foods of the 
highest order is thoroughly justified. 



Table XXI 

Composition of Various Dairy Products, Stated in Percentage 






Water 


Fat 


Protein 


Sugar 


Acid 


Ash 


Salt 


Whole milk ..... 

Skim-milk 

Cream 


87.0 
90.1 
76-54 
15.0 
90.3 
35.0 
80.0 

25.7 
4.0 


3.9 

0.1 
15-40 
81.0 

0.5 
33.0 

0.1 

10.7 
3.0 


3.2 

3.7 

2-3 

1.1 

3.4 

28.0 

18.0 

8.5 
32.3 


5.0 
5.1 

3-4 

trace 

4.4 

0.5 

1.0 

53.8 
53.8 


0.2 
0.2 
0.1-0.5 
trace 
0.7 
0.3 
0.5 


0.7 

0.8 

0.5 

0.05 

0.7 

1.3 
6.9 




Butter 


2.0 


Buttermilk 

Cheese 

Cottage cheese . . 

Condensed milk 

(sweetened) . . . 

Milk powder .... 


3^2 
0.4 



QUESTIONS 

1. Describe the physiological processes involved in making milk out of 

silage, discussing each of the constituents of the milk. 

2. What is lactic acid? How is it formed in milk? 

3. Describe the difference between casein and milk albumin as regards 

their chemical and physical properties. 

4. How does butter-fat differ from other animal fats? 



278 MILK AND ITS PRODUCTS 

."). What chemical elements are found in milk? Why do these elements and 

not some others occur in milk? 
(>. State the factors which may affect the composition of milk, and tell 

in what way they do so. 
7. Of what value are the analyses of the milk of individual cows? 
S. What chemical changes take place during the ripening of cream? 
9. What is pasteurization? What is its purpose? 

10. What weight of food materials is there in a gallon of buttermilk? 

11. What is the effect of rennin on milk? Of acid? 

LABORATORY EXPERIMENTS 

92. To Separate Pure Fat From Milk.— Moisten about 30 g. of dry, 
clean sand with about 10 g. of whole milk or cream, and place in the dry- 
ing oven at a temperature not above 100° C. When dry, crumble the 
sand, place in a filter paper in a funnel, and drip through the sand about 
50 c.c. of gasoline, ether, or carbon tetrachloride. Catch the filtrate in a 
beaker and evaporate off the gasoline. What is the residue? How could 
this method be used to determine! the amount of fat in milk ? What method 
is usually used ? How is fat usually separated from milk ? 

93. To Separate the Casein From Milk. — (a) Dilute 10 c.c. of skim- 
milk with 20 c.c. of water, add 1 c.c. of 10 per cent acetic acid, stir and 
warm gently until a curd begins to form. When it is well flocculated, filter 
through filter paper. Wash the curd with a little water. Save the filtrate, 
wh ich should be very clear, for the preparation of milk albumin in the next 
experiment. Examine the curd. Partially dry some of it, then grind with 
some sodium hydroxide, place in a test tube, and heat. The smell of am- 
monia indicates that the curd, or casein, is what kind of a compound ? 

(b) Dilute 10 c.c. of skim-milk with 20 c.c. of water, warm to about 30 
degrees, and add a little rennin solution or a portion of a "junket" tab- 
let. Let stand until the curd is well formed. Filter, and test the curd in 
the same way as that in (a). Save the filtrate for the next experiment, 
(c) What kinds of cheese are made by method (a) and by method (b) ? 

94. To Prepare Milk Albumin. — Milk albumin is the second most im- 
portant protein of milk. It is not coagulated by acid or by rennin, but is 
coagulated by heat the same as egg albumen in -experiment 88. Heat the 
filtrate from the casein in (a) and (b) in experiment 93, to boiling, and 
boil slowly until the curd forms. This curd is the coagulated milk albumin. 
It can be collected on a filter paper and tested for protein, the same as the 
casein. Save the filtrate for the next two experiments. In the making of 
cheese it this protein wasted? 

95. To Show the Presence of Sugar in Milk. — Heat a portion of the 
filtrate from the milk albumin to boiling, add a few c.c. of mixed Fehling's 
solution and boil. What sugar is present in milk? What is it used for 
commercially? What do you think would be a cheap source of it? 

96. To Show the Presence of Mineral Elements in Milk. — Evaporate 
the rest of the filtrate from the milk albumin to a small volume, transfer to 
I porcelain <iish. evaporate to dryness, and ignite to a white ash. What 
clement- make up this ash? Test for calcium and chlorine in this ash by 

ethoda used in experiments 49 (d) and . r >2 (c). 

97. To Separate the Constituents of Butter. — (a) Fill a large test 

I two-thirds full of butter. Set it in a beaker of water and heat 



LABORATORY EXPERIMENTS 279 

the latter to about 50° C. until the butter is completely melted. Allow 
to cool slowly. Several different layers of substances will be observed. 
The fat is on top, and if the cooling has been sufficiently slow, it will be seen 
to consist of both solid and liquid portions. The liquid is mostly olein, 
and the solid mostly palmitin. Below the fat is a watery layer, containing 
casein in suspension and salt in solution. How did the two latter substances 
get into the butter? 

98. To Show the Heat Test for Butter and for Oleomargarine. — Heat 
small samples of oleomargarine and of butter in spoons over the flame. 
Note the difference in the way they boil and in the amount of foaming. 

99. To Show a Difference in the Kinds of Fat in Butter and in 
Oleomargarine. — Melt a piece of butter the size of a hickory-nut in one 
test tube, and a similar quantity of nut-margarine in another. Allow the 
water and curd to settle a moment, then pour the clear fat into beakers, leav- 
ing the curd behind. Add 30 c.c of 10 per cent sodium hydroxide to each 
and boil gently for 30 minutes, replacing water lost by evaporation. Cool 
somewhat, then add 20 per cent sulfuric acid until the solution is acid. 
Carefully note the odor of the fatty acids which rise to the surface in each 
case. Of what does that of the butter remind you ? The acids which can be 
smelled are volatile. Butter-fat contains considerable volatile acids, while 
oleomargarine fat contains very little. Write equations showing the reac- 
tions that took place in this experiment. ( Compare experiment 69. ) 



CHAPTER XXI 

CHEMISTRY OF CLEANING 

The higher the stage of civilization of a people, the 
more particular are they concerning the removal of dirt 
of various sorts from their bodies, their clothes, and their 
dwellings. And the greater the care exercised in main- 
taining cleanliness, the greater is their consumption of 
soap. For soap is rightly called the universal cleansing 
agent. Since soap has been known for a very long time, 
and since it is now a cheap and common article of daily 
use, it is almost inconceivable that only a hundred years 
ago in Europe bathing was a luxury, and enjoyed only by 
the nobles and the wealthy. During the World War, soap 
became one of the scarcest of commodities in Europe, since 
all possible fats had to be converted into human foods. 
In the United States we are blessed with an abundance of 
cheap sources of soap-fat, which makes it possible for soap 
to be enjoyed by the richest and the poorest. 

Principles of Cleansing Processes. — There are in general 
three distinct methods of cleaning: 

1. The removal of dirt by emulsifying it. 

2. The removal of the dirt by dissolving it. 

3. The destruction of the color by chemical means. 

1. 4i >n is a suspension of drops of one liquid 

othi r in which it is >>>>t soluble. For example, kero- 

ifl not soluble in water: but if it is shaken violently 

with water, minute drops of it remain suspended, giving 

the water a milky appearance. This is an emulsion of 

kerosene in water. A fat or oil can be similarly emulsified 

in water. Such emulsions are not permanent, however: 

the kerosene or the oil gradually rises to the surface, the 

280 



PRINCIPLES OF CLEANSING PROCESSES 281 

fine drops unite into larger ones, and soon there is no 
longer an emulsion. If soap is dissolved in the water, the 
emulsion will remain a great deal longer. And it is this 
remarkable power of soap to make emulsions and to main- 
tain them which makes it such a valuable cleaning agent. 
For most forms of dirt in clothing and on the skin do not 
dissolve in water ; but when soap is added to the water, the 
material of the dirt is emulsified, and thus easily washed 
away in the soap solution. Then, too, soaps are weak 
alkalies ; and alkalies exert a solvent action on grease. 

2. The dissolving of stains and dirt depends upon the 
fact that some liquid can be found in which the stain is 
soluble. Thus some fruit stains will dissolve in water; 
grass stains will dissolve in alcohol; grease stains will 
dissolve in gasoline, chloroform, turpentine, and other 
similar solvents ; and paint stains will dissolve in turpen- 
tine. If the nature of the spot is known, the correct 
solvent can be applied at once. If it is not known, it is 
always best to try water first; cold water, in plentiful 
amounts, then warm water. If, after drying, the stain is 
still visible, gasoline, carbon tetrachloride (carbona), or 
benzine can be used. The stain should be rubbed with a 
cloth from the outside towards the center so as to avoid 
spreading the stain. 

3. If stains cannot be removed by emulsification or by 
dissolving out with a solvent, they can often be bleached 
to colorless compounds by chemical means. Thus oxalic 
acid removes many ink stains by forming colorless com- 
pounds ; bleaching powder removes fruit stains ; straw hats 
are bleached by sulfur dioxide (see p. 135) ; yellowness in 
cloth is readily removed by the action of sunlight ; hair and 
other substances can be bleached by means of hydrogen 
peroxide. Usually the nature of the stain should be known 
before a bleaching agent is tried. Also, the possible effect 
of the reagent on the material to be bleached should be 



282 CHEMISTRY OF CLEANING 

known, or found out by trial on a small sample. In the 
case of colored fabrics this is important, for an acid may 
destroy the color, and an alkali restore it, or vice versa. 
Ammonia water and weak vinegar can be used for alkali 
and acid, respectively, in such cases. 

Soaps. — As has been discussed in a former chapter, 
soap is made by boiling a fat with an alkali : 



C 3 H B ( CisH^Oo ) 3 


+ 3NaOH = 


C 3 H B (OH), 


+ 3 NaC 18 H 35 : 


stearin 


sodium 


glycerin 


sodium 




hydroxide 




stearate 
( soap ) 



Thus one molecule of fat (in this case stearin of beef or 
mutton suet) combines with three molecules of alkali to 
produce one molecule of glycerin and three molecules of 
soap. Soap is the sodium or potassium salt of a fatty acid. 
The commonest fatty acids in fats that can be used for 
soap-making are palmitic, stearic, and oleic; as the latter 
makes a soft soap, only a small amount of it can be present 
in a soap fat. Potassium soaps are soft. The soft soap 
of our grandmothers was made from potassium carbonate 
leached from wood ashes. 

The above equation tells us that definite amounts of fat 
and alkali react. If more than the correct amount of fat is 
used, it will remain as fat in the soap and make the latter 
greasy. If more than the correct amount of alkali is used, 
the resultant soap will be alkaline, and it will have a caus- 
tic action on skin and on cloth. Therefore, the process of 
soap-making is subjected to careful chemical control. 

Glycerin is always formed as a by-product. It is re- 
moved from the soap, as it is a valuable raw material for 
explosives and other commodities. In the so-called glyc- 
erin soaps a portion of the glycerin is put back into 
the soap. 

Composition of Commercial Soaps. — Although soap is 
essentially a mixture of sodium salts of fatty acids, there 



HARD WATER 283 

are numerous other substances found in the soaps on 
the market. Water constitutes from 15 to 35 per cent of 
them; the softness of many soaps, and the rapidity with 
which they wear away in water, are due to their high water 
content. Practically all soaps contain perfume. In some 
cases this is added to masque the odor of rancid fats used 
in the manufacture, but more often the perfume adds to 
the attractiveness of the product, and certain perfumes 
act as preservatives for the soap by preventing moldiness. 
The most common adulterants of soaps are the so-called 
fillers. These are usually heavy, inactive substances such 
as chalk, infusional earth, sodium sulfate, and water- 
glass, added to the soap to give it weight. Alkaline soaps 
are those which contain sodium or potassium carbonate. 
These are undesirable constituents, since they are harsh 
on the hands and on fabrics. Very often substances of 
supposed medicinal value are added, such as tar and car- 
bolic acid. Again, there are many scouring soaps and 
scouring powders on the market; these consist largely 
of sodium carbonate and soap, with pumice as an abrasive. 
Sometimes borax, naphtha, or kerosene is added to soap ; 
these increase its cleaning power. 

Hard Water. — Hard water is one of the most frequent 
causes of the uneconomical use of soap. The calcium and 
magnesium of the water combine with the soap to form 
lime soap and magnesium soap : 

2NaC 18 H 35 2 + MgS0 4 = Mg ( C 1S H 35 2 ) 2 +Na 2 S0 4 
soap magnesium magnesium sodium 

sulfate stearate sulfate 

The magnesium and calcium soaps are insoluble, and form 
the sticky, gummy wads so familiar to users of hard water. 
This reaction consumes the soap, so that more must be 
added to get a cleansing effect. 

There are several ways of softening water. If the 
water has only temporary hardness, it may be removed 



284 CHEMISTRY OF CLEANING 

by boiling | p. 102). As this requires fuel, a cheaper method 
consists in adding washing soda. It reacts as follows : 



CaS0 4 


+ 


Na,C0 3 = 


= CaC0 3 


+ 


Na,S0 4 


calcium 




sodium 


calcium 




sodium 


sulfate 




carbonate 


carbonate 




sulfate 



The calcium carbonate being insoluble in water settles to 
the bottom. The sodium sulfate does no harm. There is 
thus nothing left in the water to react with the soap. 
Before soap is added to hard water for laundering pur- 
poses, the water should be softened by the addition of 
washing soda. Much less soap will then be required to 
produce a suds. On a large scale water is softened in 
tanks by adding washing soda, allowing the precipitated 
calcium carbonate to settle to the bottom, and then draw- 
ing off the clear, soft water ; or, in the case of large city 
water works, the sediment is removed by nitration. 

QUESTIONS 

1. How does soap act in removing dirt from cloth or from the skin? 

2. Does soapy water dissolve fats? 

3. What is meant by an emulsion? Is milk an emulsion? Why? 

4. State two ways in which a grass stain might be removed from cloth. 

5. What kinds of spots are best removed by gasoline, carbona, and chloro- 

form? By water? By turpentine? By bleaching powder? 
0. What is a soap? What is the source of glycerin? 
7. Why are "fillers" added to soap? 
s. Why are perfumes added to soap? 

9. Why do the leachings from wood ashes make a soft soap? 
10. Explain the action of hard water on soap. How can this be prevented? 

LABORATORY EXPERIMENTS 

ioo. To Remove Stains by Bleaching. — Make stains on pieces of cotton 
cloth with green grass, grape juice, red ink, and ordinary writing ink. Test 
tin- elfectiveness of warm oxalic acid solution, hydrogen peroxide, bleach- 
ing powder solution, and alcohol in removing them. Compare the bleaching 
action of sulfur dioxide in experiment 46, and of chlorine in experiment 49. 

101. To Test the Effect of Alkalies and of Acids on Various Col- 
ored Fabrics. — Collect a number of samples of colored goods of both cotton 
and >ilk and test the decolorizing effect of a drop of 5 per cent acetic acid 
and of a drop of 5 per cent of ammonia on each. Also test the restoring 
action of the acid on color removed by the alkali, and vice versa. Record the 
color of each piece, of goo'ds before treatment, after treatment with acid, 
and after t rea t ment wit h ammonia. 



APPENDIX 

LIST OF REFERENCES TO SUPPLEMENT THIS TEXT. 

Descriptive Chemistry. Newell. D. C. Heath & Co., Boston. 

Chemistry of Common Things. Brownlee, Fuller, Hancock and Whitsit. 
Allyn & Bacon, Boston. 

The Living Plant. Ganong. Henry Holt & Co., New York. 

Productive Soils. Weir. Lippincott, Philadelphia. 

Barnyard Manure. Beal. Farmers' Bulletin 192, U. S. Department of 
Agriculture, Washington, D. C. 

Feeds and Feeding. Henry and Morrison. Published by the Authors, Madi- 
son, Wis. 

Productive Feeding of Farm Animals. Woll. Lippincott, Philadelphia. 

Principles of Human Nutrition. Jordan. Macmillan, New York. 

Function and Uses of Food. Langworthy. Circular 46, U. S. Department 
of Agriculture, Office of Exp. Sta. 

Successful Canning and Preserving. Powell. Lippincott, Philadelphia. 

Bread and Bread Making. Atwater. Farmers' Bulletin 389, U. S. Depart- 
ment of Agriculture, Washington, D. C. 

Some Common Disinfectants. Dorset. Farmers' Bulletin 345, U. S. Depart- 
ment of Agriculture, Washington, D. C. 

The Chemistry of Cooking and Cleaning. Richards and Elliott. Home 
Science Pub. Co., Boston. 

Home and Community Hygiene. Broadhurst. Lippincott, Philadelphia. 

Dairy Chemistry. Snyder. Macmillan, New York. 

LIST OF APPARATUS REQUIRED 

For each ten students 
1 balance, sensitive to 0.01 g. 
1 set of weights, from 100 g. to 0.01 g. 
1 hot air oven, about 10 x 10 x 12 in. 
1 hot water oven, about 12xl2xl4in. inside 

1 500 c.c. cylinder 

2 porcelain or glass mortar and pestles. 
1 set cork borers 

Several dozen assorted rubber and cork stoppers 

1 magnet 

2 pneumatic troughs 

4 files, round and triangular 

4 wing-top burners 
20 feet rubber tubing, 5 mm. inside diameter 
30 feet glass tubing. 5 mm. inside diameter 

4 thermometers, 0° to 120° C. 

1 condenser (Liebig) 

2 bell jars, 8 in. diameter, open at top 

1 apparatus for electrolysis of water (optional) 

4 florence flasks, 1000 c.c. 

4 deflagrating spoons 
10 feet aluminum wire, 2 mm. 
V-2 pound copper wire, No. 20 

285 



286 CHEMISTRY OF CLEANING 

For each student 

1 Bunsen burner and tubing, or alcohol-lamp 

1 ring stand and rings 

I filt or arm 

1 test tube holder 

1 test tube brush 

1 test tube clamp 

1 test tube rack 

1 asbestos wire gauge 

1 pair tongs, 9 inches 
25 filter papers, 9 cm. 

2 porcelain evaporating dishes, 3 in. 
12 test tubes, 6 in. 

4 bottles, wide mouth, 8 oz. 
4 glass plates, 4 in. 
4 beakers, 400 c.c. 

2 beakers, 100 c.c. 

1 florence flask, 400 c.c. 
I funnel, 2 in., long stem 

1 funnel, 2 in., short stem 

3 watch glasses, 4 in. 

2 stirring rods, 6 in. 
1 box matches 

1 cylinder, 100 c.c. 
1 cylinder, 25 c.c. 

Chemicals required by class of ten Grams 

Acid, acetic ( 50 per cent. ) 200 

hydrochloric (sp.gr. 1.2) 2000 

nitric (sp.gr. 1.4) 1000 

sulfuric (sp.gr. 1.8) 2000 

tartaric 150 

oxalic 20 

butyric 25 

salicylic 20 

molybdic 25 

Alum 15 

Alcohol, grain ( ethyl ) , 500 

wood (methyl) 200 

Ammonium hydroxide (sp.gr. 0.9) 1000 

tartrate 10 

chloride 200 

Barium chloride 100 

Bleaching powder 100 

Carbon bisulfide 500 

tetrachloride .' 100 

Calcium chloride 400 

carbonate 100 

sulfate 300 

phosphate (tri-) 300 

(acid) 100 

hydroxide 100 



LIST OF APPARATUS REQUIRED 287 

Grams 

Cochineal 10 

Charcoal, stick 30 

Copper sulfate 150 

oxide 50 

Dextrose 40 

Ether, 700 

Formalin 200 

Ferrous sulfate 100 

Hydrogen peroxide 100 

Iodine 20 

Iron filings 500 

wool 200 

wire, picture 100 

Litmus paper, blue and pink 

Lactose (milk sugar ) 50 

Lead acetate • 10 

Maltose (malt sugar) 50 

Methyl orange 10 

Manganese dioxide 30 

Magnesium ribbon 100 

sulfate 100 

chloride 100 

Mercurous chloride 20 

Mercuric oxide 100 

Phenolphthalein 10 

Phosphorus, yellow ' 50 

Pepsin 10 

Potassium chloride 100 

nitrate 25 

iodide 10 

permanganate 100 

hydrogen phosphate 50 

chlorate 100 

sulfate 100 

oxalate 20 

Rochelle salt 200 

Silver nitrate 20 

Sulfur 500 

Sodium nitrate : 500 

sulfate 100 

hydrogen phosphate 100 

hydroxide 500 

Tannin 20 

Zinc (flakes or granulated) 500 

The above list does not include various common commodities which do 
not have to be bought through a chemical supply house, such as common 
salt, vinegar, sugar, seeds, various fruits and vegetables, baking soda 
quicklime, limestone, soap, yeast, kerosene, gasoline, eggs, tea, copper wire, 
sand, Mason jars, starch, flour, linseed oil, cottonseed oil, and milk. 



288 CHEMISTRY OF CLEANING j 

■ 
THE METRIC SYSTEM 

10 millimeters (mm.) =1 centimeter (cm.) 
10 centimeters =1 decimeter (dm.) 

100 centimeters =1 meter (m. ) 

1000 cubic centimeters (c.c.) =1 liter (1.) 
1 cubic centimeter of water = 1 gram (g. ) 

1000 grams =1 kilogram, or kilo (kg.) 

CONVERSION OF METRIC INTO ORDINARY UNITS 

1 yard =91.6 cm. 1 meter = 39.3 inches 

1 inch = 2.54 cm. 1 cm. = 0.39 inch 

1 quart = 1134 c.c. 1 liter = 0.88 quart 

1 oz; = 28.3 g. 1 g. = 15.4 grains 

1 lb. = 453.6 g. 1 kilo = 2.2 lbs. 



INDEX 



Acetylene, 56, 57, 72 
Acid, acetic, 47, 75, 85 
- butyric, 76 

carbolic, 50 

carbonic, 18, 85, 132 

citric, 217 

fatty, 76 

formic, 75 

hydrochloric, 85, 140 

hydrocyanic, prussic, 77, 78, 120 

lactic, 76, 217, 272 

malic, 76, 217 

muriatic, 140 

nitric, 20, 85 

oxalic, 76, 217 

phosphate, 139, 190, 198, 261 

phosphoric, 84, 85 

tannic, 111, 116, 225 

tartaric, 76, 85, 217, 261 
Acids, definition of, 84-85 

formation of, 83, 128 

plant, 217, 228 

properties of, 85, 93 
Acrolein, 256 

Albumin of milk, 272, 278 
Alcohol, as fuel, 54 

ethvl (grain), 74, 82 

methyl (wood), 47, 74 
Aldehydes, 73 
Alkalies, definition of, 87 

formation of, 86, 128 

properties of, 86, 87, 93 
Alkaloids, 219, 228 
Alum, 107, 261 
Aluminum, 105, 110 

oxide, 107 
Amalgam, 121 
Amides, 219, 228 
Ammonia, 50, 129, 144 

from manure, 186 
Ammonium, carbonate, 130 

chloride, 130 

hydrate, 86, 129 

sulfate, 50, 130, 189 
19 



Animals, composition of, 229 

elements necessary for, 148-150 
153 
Apatite, 137, 158 
Apparatus, list of required, 286 
Argyrol, 123 
Arsenic, 141 

insecticides, 120 
Asbestos, 141 
Ash, 247, 254 

of milk, 273 
Assimilation, 239 

Atmosphere, composition of, 16, 17, 
18 

extent of, 16 
Atomic weights, 7, 11 
Atoms, 9 

Bacteria in soil, 175 

in water, 40 
Baking powder, 261, 269 
Basic slag, 190 

Bedding, effect on manure, 185 
Benzaldehyde, 74 
Benzine, 72, 281 
Benzoic acid, 267 
Benzol, 72 
Bile, 238 

Bleaching powder, 104, 140 
Bleaching with sulfur, 136 

of stains, 284 
Blood corpuscles, 116 

dried, 189 
Bluing, laundry, 116 
Blue vitriol, 119 
Boiling of foods, 257 
Bones, composition of, 244 

ground, 190 
Boric acid, 267 
Brass, 119, 121 
Bread, 259, 260 
Bricks, 107 
Brimstone, 134 
Bronze, 118 
Butter, 276-279 
Butter-fat, 273, 278 

289 



1 



290 



INDEX 



Caffeine, 219 
Calcium, 99, 152 

carbonate, 99, 159 

hydrate, 86 

nitrate, 129, 189 

oxide, 100 

phosphate, 104, 137, 139 

silicate, 104 

sulfide, 104 
Carbide, 69, 104 
Carbohydrates, 205-214, 227 

effect of heat on, 257, 269 
Carbon cycle, 66, 78-79 

forms of, 61 

occurrence of, 61, 78-80, 81, 152 

battery, 65 

chemistry of, 77-80, 132 
Carbonates, 132 
Carbon bisulfide, 70 
Carbon dioxide, formation from car- 
bonates, 58, 65, 81, 132 
in air, 18, 26 

produced in body, 59, 242 
relation to plants, 23 
test for, 26, 81, 111 
used by crops, 19 
Carbon monoxide, formation of, 68 

properties of, 68 
Carborundum, 69 
Casein of milk, 272, 278 
Caves, formation of, 103 
Celluloid, 131 
Cellulose, 211 
Chalk, 66, 99 
Changes, chemical, 2, 14 

physical, 2, 14 
Charcoal, 62-65 

kinds of, 64 

properties of, 64, 81 
Cheese, 276, 277 
Chemicals, list of required, 287 
Chemistry, early, 5 

field of, 5, 71 

organic, 70-72 
Chlorides, 152 
Chlorine, as disinfectant, 41, 140 

occurrence of, 140 

properties of, 145 
Chlorophyll, 203, 218 
Clay, 106-108, 163 
Cleaning, chemistry of, 280-285 



Coal, composition of, 53 

destructive distillation of, 47, 49, 
60 

formation of, 50 
Coal-gas, 47, 48, 49 
Cocaine, 219 
Coke, 50 
Collodion, 131 
Colored fabrics, 284 
Coloring matter, 218, 228 
Combination, chemical, 15 
Combustion, definition of, 22, 25. 44 

in body, 242 

of wood and coal, 46 
Compounds, chemical, 4 

in animals, 226-228 

in plants, 204 
Copper allovs, 119 

fungicides, 118, 120 

hydrate, 117 

sulfate, 119 

ore, 125 

properties of, 117 
Cotton, 211, 212 
Cow, as a chemical factory, 271 
Cream, 276, 277 
Cream of tartar, 217, 261 
Creosote, 50 
Crude fiber, 247, 254 

protein, 247 
Cyanamide, calcium, 77 

Decomposition, chemical, 15 

Denitrification, 174 

Dextrin, 211 

Dextrose, glucose, 82, 207, 213, 257 

Diamond, 61, 62 

Digestibility, coefficient of, 245 

Digestion, of food, 236 

in mouth, 237 

in intestines, 238 

in stomach, 237 
Di-hexoses, 208 
Distillation, destructive, 47, 48, 49. 60 

industrial uses of, 38 

of water, 37 



Earth, origin of, 155 
Egg shells, 244 

white of, 244, 262 
Electrolysis of water, 29 



INDEX 



291 



Elements, agricultural chemical, 147, 
151 

chemical, 4, 6, 7 

in soil, 148 

most abundant, 8 

necessary for plants and animals, 
148-150, 153 
Emulsions, 280 
Enzymes, 235, 236-238 
Epsom salts, 105 
Equations, chemical, 10, 12, 13 
Esters, 76, 82 
Ether extract, 248, 254 
Explosives, 21, 131 
Extract, ether, 248, 254 

nitrogen-free, 248 

Fats and oils, 214-217, 227 

decomposition of, 215 
effect of heat on, 256 
in butter and margarine, 279 
occurrence in seeds, 225, 254 

in meat, 230 
properties of, 224 
Feed, effect on manure, 184 

on milk, 275 
Feeds, analysis of, 246 

composition of, 250 
Feldspar, 158 
Fermentation, alcoholic, 74, 82 

of manure, 186, 198 
Fertilization, systems of, 195 
Fertilizer plots, 195 
Fertilizers, choice of, 194 

commercial, 181, 188-197 

effects of, 183, 195 

mixed, 193 

need of, 180 

nitrogen, 188 

phosphorus, 189 

potassium, 190 

terms used in, 193 
Fiber, crude, 247 
Filtration of water, 35-37 
Fire extinguishers, 56, 58 
Fish scrap, 189 
Flame, definition of, 45 

from wood, 47 

study of, 59 
Flashlight powder, 105 
Flax, 212 
Floats, 139 



Food, amount required, 232 

analysis of, 246 

composition of, 249 

digestion of, 236 

from animal sources, 241 

function of, 231 

preservation of, 262 
Fools' gold, 136 

Formaldehyde, as food preservative, 
267 

formation of, 73, 82 

in plants, 73 
Formulas, chemical, 12 
Fructose, levulose, fruit sugar, 206, 

207, 213 
Frying of foods, 257 
Fuel elements, 72 

gaseous, 47-49, 54, 56, 57, 72 

liquid, 53-54 

solid, 50-53 
Fungi, 203 
Fungicides, 118, 120 

Galactose, 207, 213 
Galvanized iron, 121 
Gas, acetylene, 56, 57 

coal, 47-49 

natural, 54 

removal of, from water, 39, 43 

water, 54 
Gasolene, 72 
Gastric juice, 237 
Gelatin, 219, 244 
Germination of seed, 219 
Glaciers, 160 
Gluten, 219, 225 
Glycerin, 75, 215, 282 
Glycogen, 211 
Gold, 123 

mining, 121 
Graphite, 62 
Gums, 206 

Hard water, 34, 102, 283 
Health, maintenance of, 235 
Heat and energy, production of, 231 
Heat, effect on food, 255-258, 268, 

269 
Hematite, 112 
Hexoses, 206 



292 



INDEX 



Humus, 167, 170 

formation of, 171 

properties of, 171, 172 
Hydrocarbons, 72 
Hydrogen, compounds of, 31 

preparation of, 30, 42 

properties of, 31, 127 
Hydrogen peroxide, 32 

sulfide, 137 
Hydrolysis of carbohydrates, 213, 225 
Hypochlorite of lime, 41, 104 

Indicators, 94 

Ink, preparation of, 111, 116 

Insecticides, 120 

Iodine, 141 

Iodoform, 141 

Iron, age of, 112 

citrate, 116 

galvanized, 121 

hydrate, 86 

kinds of, 115 

oxides, 112 

pyrites, 159 

rust, 125 

smelting of, 113 

sulfate, 111, 116 

tannate, 116 

Kainit, 191 
Kaolin, 158 
Kerosene, 72 

Lactose, 210, 213, 272, 278 
Lard substitutes, 217 
Lead, 116, 117 

arsenate, 117, 120 

hydrate, 86 

sulfate, 117 

sulfide, 116 

white, 117 
Leavening agents, 258 
Legumes, nitrogen fixation by, 176 

inoculation of, 177 
Levulose, fructose, fruit sugar, 206, 

207, 257 
Lite origin of, 151, 156 
Lime, milk of, 101 

plaster, 101 

slaking of, 101, 111 
Lime sulfur, 136 
Limestone, 66, 99, 191 
[dmewater, 101 



Limonite, 159 
Linen, 212 
Litmus, 84 
Living cells, 132 
Loam, 163 



Magnesium, 104 

carbonate, 105, 159 

oxide, 105 ' 

sulfate, 105, 136 
Magnetite, 112 
Maltose, 210, 213 
Manure, 180 

barnyard, 181-187 

composition of, 182-186 

fermentation of, 186 

green, 187 

losses of, 187 

rotting of, 186 
Marble, 66, 99 
Margarine, 217, 279 
Matches, 138 
Meat, cooking of, 257 
Mercuric chloride, 122 

fulminate, 122 
Mercurous chloride, 121 
Mercury, 121, 126 
Metals and non-metals, 90, 95, 127 
Metals, alkali, 95 

alkaline earths, 95, 99 

heavy, 112-126 

light, 95-111 
Metric system, 289 
Mica, 158 
Milk, 270-279 

composition of, 272-276 

preservation of, 269 

sugar, 210, 278 
Mineral matter, in animals, 227 
in milk, 278 
in plants, 205 
Minerals, 157-159, 171 
Moisture, 246, 254 

and food preservation, 264 
Molecular weights, 1 1 
Molecules, 9 
Morphine, 219 
Muck, 163 

Muriate of potash, 191 
Mushrooms, 203 
Mustard gas, 137 



INDEX 



293 



Neutralization, 88 

by carbonates, 133 
Nicotine, 219 
Nitrates, 129, 173 

as fertilizers, 129 
Nitric acid, from lightning, 20, 128, 
129 
preparation of, 20, 144 

properties of, 144 
Nitrification, 173 
Nitrogen, fixation in soils, 174 

in air, 19, 22, 27, 128 

in fertilizers and manures, 198 

in soil, 174-179 

properties of, 19 
Nitrogen-free extract, 248 
Non-metals, 127-146 v 
Nutritive ratio, 252 

Oils and fats, 214-217 

drying of, 225 

mineral, 54, 215 

volatile, 76, 218, 228 
Oxidation, 25 
Oxides, 128, 141 
Oxygen, 22 

in air, 23 

preparation of, 27 

properties of, 25, 27, 127 

Painters' sickness, 117 
Pancreatic juice, 238 
Paraffine, 73 
Peat, composition of, 53 

formation of, 51 

soils, 163-164 
Pentoses, 206 
Pepsin, 237, 244 
Petroleum, 54 
Pewter, 119 

Phosphates, 139, 152, 189 
Phosphorescence, 137 
Phosphorus, 137-140, 145 
Photosynthesis, 25. 203 
Plant food, available, 168 

in soil and air, 200 
loss from farm, 181 
total, 167 

juices, 225 
Plants, as chemical factors, 200-202 

compounds in, 204 

elements necessary for, 148-150, 
153 

importance of, 199, 226 



Plaster, lime, 101 

of Paris, 103, 111 
Platinum, 124 
Polyhexoses, 210 
Portland cement, 103 
Potassium, 98 

carbonate, 98 

chloride, 98, 191 

cyanide, 98 

hydrate, 86, 98 

nitrate, 98, 129 

sulfate, 98, 136, 191 
Preservatives, food, 262-268, 269 
Protein, 218, 228, 244 

crude, 247 

effect of heat on, 255, 268 
Pumice, 141 
Ptyalin, 244 

Quartz, 158 
Quicklime, 99, 111 
Quinine, 219 

Radicles, 89, 92 

Ration, balanced, 253 

Refrigerating plants, 130 

Rennin, 237 

Roasting of foods, 257 

Rock phosphate, 137, 139, 189, 198 

Roots, absorption by, 148 

Saleratus, 97, 132, 261 

Saliva, 237, 244 

Salt, preparation of common, 94 

as preservative, 267 
Saltpeter, 97, 129, 267 
Salts, definition of, 88, 90 

formation of, 87 
Sand, 163 

Seeds, germination of, 219 
Selenite, 159 
Silicates, 141 
Silicon, 140 

dioxide, 140, 158 
Silk, 212 
Silver, 122 

bromide, 122 

chloride, 122 

German, 119 

mining, 121 

nitrate, 126 
Smoke, as a preservative, 265, 267 



294 



INDEX 



Soap, 97 

making, 215, 224, 282 

as cleaning agent, 281-283 
Soda, 261 
Sodium, 96 

bicarbonate, 97, 132 

borate, 97 

carbonate, 97, 132 

chloride, 94, 97 

cyanide, 98 

hydrate, 86, 96 

hyposulfite, 97 

nitrate, 97, 129 

silicate, 97 

sulfate, 97, 137 
Soils, 155-179 

acid, 133, 178 

acidity of, 178, 192 

amendments for, 191 

analysis of, 168 

chemical changes in, 171-179 

composition of, 148, 166-169 

elements in, 148, 169 

factors in fertility of, 169 

flocculating of, 165, 179 

formation of, 157-162 

kinds, 162-165 

mechanics of, 165, 170 

origin of, 156 

puddling of, 165 

warm and cold, 166 
Solder, 119 

Solubilities, table of, 146 
St; i ins, removal of, 284 
Starch, 210, 223, 244, 257, 269 
Stassfurt mines, 191 
Steel, 115, 116 
Sterilization with heat, 263 
Strychnine, 219 
Subsoil, 163 
Sucrose, 208, 213, 257 
Sugar, as food preservative, 266 

beet, 208 

cane, 208 

fruit, 207 

grape, 207 

matt, 210 

milk, 210, 272, 278 
Sugars, occurrence of, 224, 230, 278 

properties of, 223 
Sulfates, L36 

Sulfides, 136 



Sulfur, 133-137 

dioxide, 135, 144 
Sulfuric acid, 136, 144 
Superphosphate, 190 
Symbols, chemical, 7, 9 

Talc, 141, 159 
Tannin, 111, 116, 225 
Temperature, effect on micro-organ- 
isms, 262, 269 

kindling, 45, 56 
Thermite, 107 
Tin, 119 
Tinware, 119 
Tissue, building of, 234, 240 

repair of, 232 
Toluol, 72 

Urea in the body, 242 
in manure, 186 

Valence, 90-93 
Vegetables, cooking of, 257 
Venetian red, 116 
Vitamines, 234 

Waste, elimination of, 240 
Water, composition, 29 

distillation of, 37, 43 

electrolysis, 29, 42 

filtration of, 35-37 

glass, 141 

hard, 34, 102, 283 

importance of, 28, 201 

impurities in, 33, 34 

in air, 27 

in plant and animal tissues, 39, 
42, 201, 226, 230 

purification of, 34-43 

requirements of plants, 201 

solvent power of, 33, 43 

synthesis of, 32 
White lead, 117 
Winds, 162 
Wood, ashes, 191 

destructive distillation of, 47, 48 
Wool, 212 

Yeast, 258 

Zinc, 121 

oxide, 121 









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